Edited to add: Apparently I'm the only one here who needs lessons in brevity. :P

I've used 3 different tablet PCs, so I can at least compare to that experience for you:

1. JOURNAL:

The Journal program on the edge is quite comparable to the Journal program on Tablet PCs. I don't think you'll find much difference at all, except for navigation of menus. I use this program continuously throughout the day and have yet to have it crash on me. It's very stable and if you write on the blank background, there really is no lag at all. (Sometimes, the more there is on the background the slightly increased the lag becomes. Even then, I wouldn't say the lag is bad.) You do need to be aware, though, that handwriting recognition is not yet supported. So while you can write, the edge itself can't convert that to text. Not sure whether that's a deal breaker for you, and I think I mention below that with the help of Evernote on a PC I believe someone here has been able to get handwriting recognition.

Depending on which tablet PC you've used, one that requires a special pen or one that is simply a touch screen, the fact that your hand can touch the screen while you're writing without screwing up your notes might be a pleasant surprise. I much prefered my tablets that were not also touch screens with any surface, especially since I'm left handed.

I'm actually finding I'm now using the program in a way I didn't expect: I have my machine set up like a laptop (as if the e-ink side were the keys) and I write notes in landscape (even though that orientation isn't supported.) It really doesn't make much of a difference since all the icons are on the top/bottom (or for me, the two sides) and whether I see them rotated at 90 degrees or not doesn't make a big deal. So I mostly use the machine in "laptop mode" with an electronic writing surface. I can jot down notes while viewing web pages, reminders, etc. Without losing focus on my main window. In this way, the journal is actually better than a tablet PC, I really do find.

2. READING PDFS

I haven't yet had any trouble reading pdfs. Most of what I read are word documents exported as pdfs, scans of documents like our mail, and web pages printed as pdfs (sometimes after having gone through something like "readability" to strip out the non-text stuff). Some people here are better able to comment on quirks with zooming etc., but I really haven't had any trouble.

3. ANNOTATING PDFS

With the exception of highlighting, I haven't noticed much of a difference between how I would import a Pdf into Windows Journal note and write comments (I edited student papers that way) and opening up a pdf to add handwritten comments on the edge. Highlighting is better than it was on Day 1, but it's still tricky to get exactly what you want highlighted (it really does seem to depend on the formatting of the document and what the pdf treats as a "word" or "line"). It usually takes me 2 - 4 times to get only and exactly what I want highlighted, and I usually only care about highlighting when I want to add entries to the "table of contents." A very cool feature of the highlighting tool is that even for documents without tables of contents, one is created by adding highlights. (So, you can look at the TOC for a quick glance of bookmarks to everything highlighted.) This is great for an article "10 reasons to..." and if you highlight on 1. Reason #1 and 2. Reason #2 then you'll make your own TOC you can access. WIndows Journal doesn't do this, but maybe Evernote, GoBinder etc. do have this feature. If I don't care about a TOC, then instead of highlighting I usually just choose to underline or otherwise make handwritten annotations because it's quicker than getting the highlighting just right! I haven't had to print an annotated pdf yet (eg give back to a student with corrections); I've only exported handwritten journals/diagrams to pdf. I think Cheyennedonna commented recently about annotations showing up when you print/export, so I believe it works.

4.TYPING ON THE VIRTUAL KEYBOARD

It works, but I find it a tad too small and a notch too unreliable to do much touch typing. For the most part, I have an external keyboard connected to my machine. If I do use the virtual keyboard, it's usually by tapping with the stylus. Certainly, typed notes pales in comparison to handwritten notes. I still have never gotten around to using Evernote, but I believe someone commented that you can export your handwritten notes and have them OCR'd by Evernote. But, I don't think there's been a tablet PC virtual keyboard that really functioned much better. So in comparison to that of a tablet PC, I don't think you're sacrificing much.

5. OVERALL-COMPUTERISHNESS

The one thing to keep in mind compared to a tablet PC is that a tablet PC really is a full-blown personal computer. It runs windows, and therefore has a very common operating system as well as almost all the programs you could ever want. App selection is much more limited on the edge, and the apps that it does have are really meant to be used one at a time. (Although several do run in the background, it's just that you can only ever see one app on the screen at once - there's no concept of resizing windows to see two programs at once.)

That being said, I'm actually without any other machine right now and I'm using the edge as my only laptop/computer. So, there's very little in terms of essentials (web, email, twitter, documents) it can't do compared to a tablet PC, and some that, in my opinion, it does just as well or better. I love that the journal/pdf annotation is its own screen and the other is free for other apps running. I love the clamshell design and multiple positions it can be used in. I love. That it's one-click to turn a web page into a pdf or epub, since a lot of what I used to do was print articles off the web.

One of the reasons I felt comfortable taking the chance and pre-ordering when it first came out was because it seemed to be a true tabletPC-lite at 15-25% of the cost. (I've been on a mac for the last 3 years and missed tablet PC functions.) We are paperless at home (house sitter scans us email, we have fax to email services, use tablets to sign documents) and living much of the time on the road demands it. I've used the edge to sketch a quick floor plan and email it to a designer; to annotate a map with directions and landmarks for a friend coming to visit, to sign credit card authorization forms and fax via email... all without a bloated operating system. That being said, I've had to settle for a more app-based, minimal operating system, but my restrictions have been more like, "I wish there was a way to do this," instead of, "Windows needs your permission to continue," or a blue screen of death. It might be fair to say that with a tablet PC you might find yourself battling more with the software/OS, and with the edge you might find yourself battling more with the hardware. (It's not as "sleek" an experience as an iPad, for example, and seems a little clunky physically.) At least that's been my experience - my software/OS issues have more revolved around finding an app to do what I want rather than getting an app to work. Others might have different experiences.

Even as my only computer, this machine is holding up pretty well, and I would choose it over a tablet PC all things considered. In just the 6 or 7 months it's been out, there have already been noticable improvements. But, the people who are most satisfied with the device are those who don't mind that it takes 2 minutes to turn on or that you have to get used to a variety of buttons/menus. You really do have to want the unique features it does have (pdf/annotation/handwriting) because it helps you forgive some other little quirks (highlighting). It's still has the feel of a first generation device (physically) but there are lots of us here who absolutely love this thing. I don't think you'll find this feature set at this price anywhere else.