I thought I might as well write up my experience in rooting the Nook Simple Touch.
I only actually used an ereader for the first time a few weeks ago. Seemed so much easier to concentrate than reading on a laptop screen, so I looked into which devices were available. I decided to get a NST due to the (apparently) better screen refresh and because it was rootable. (For Australians and NZers, root has quite a different meaning by the way
I don't live in the States, so I picked up a grey import from an online retailer. It all registered OK, but I haven't put in a credit card yet. Just skipped that step, not really planning to buy from B&N. The NST they sent was Nook OS version 1.1
I went back to Nook Devs to find the procedure for rooting that I had read about when researching the purchase. However, I misremembered and assumed that their page "Nook Rooting Manual" was a manual on how to root, when what they meant was it is the non-automated way to root. So I went through the noogie manual rooting process, got to the end and then didn't know really what to do. You have to install the Android developers kit and transfer over a launcher, I think. But of course I then realized that I had forgotten about the Touch Nooter method, and started again. Still, at least now I know how to use noogie, and I made a clean backup image of the internal disk in its original state using that.
I actually put Ubuntu onto a pen drive to do all this rooting, as it seemed simpler. Ubuntu (Pangolin) seems really great, but unfortunately something broke and it stopped recognizing my video card and stopped booting. And I had put my clean backup image on the pen drive! But luckily it wasn't on the Ubuntu partition so I was able to recover it by booting off a CD of Ubuntu and accessing the other partition. What a hassle, but the clean backup did survive.
I did the Touch Nooter process, which all went smoothly. However, this is my first ever Android device and I didn't really know what was going on with the OS. It all seemed quite ugly and clunky. Animations look bad on the e-ink screen and so do the default icons. I also didn't want Button Savior when booting to the vanilla Nook OS, because it is distracting. Of the three buttons on the Android dock, the app drawer worked, but the browser just force-closed and the other icon said to drag stuff onto it, but dragging doesn't seem to work on the ADW launcher desktop, so the dock seemed pointless also. And the status bar kept disappearing, which caused problems.
So I went through all the settings, turned off all animations, changed the desktop icons to the "minimalist black" theme, turned off the gesture commands that were hiding the status bar by accident, turned off the dock (I put an icon on the desktop to open the app drawer), changed the wallpaper to plain white, and generally got rid of all the bells and whistles and made things easier to see in black and white (e.g. mid-grey app drawer background). Now it looks very clean.
I like to boot up fresh into Android or the Nook OS depending on what I am doing, so Button Savior was only useful for exiting certain apps. What I decided to use instead is a utility called "Processes" that is part of the Astro file manager. I switch to this by holding down the Nook button for a couple of seconds to bring up the "recent apps" menu. If an app doesn't have an exit button (e.g. IMDb where you have to press the back button on the status bar and back all the way out of the app) I just kill the process. This means I can do without Button Savior (but if I ever accidentally set the Nook OS as the default boot OS, I will have to re-root).
One reason I wanted to root was to read PDFs, because the Nook reader app has little functionality for PDFs. Often the text won't reflow or reflows really badly, so you need to be able to see the full width of the page at decent magnification. I found an app called Rotation Locker that lets you change to landscape orientation, and I try to also keep this in the "recent apps" menu. Of the two free PDF apps I tried, BeamReader seemed to display things better, so I use that in landscape orientation, and PDFs are pretty easy to read. I keep the desktop in landscape and generally run all apps this way. Some will occasionally revert to portrait, but I bring up the "recent apps" menu and force them back.
For the browser, the only one I could get to work was Opera Mobile. However, this is a bit heavy for the screen. Luckily, someone on XDA put up a package of an old version of Opera Mini, which worked fine. This tries to load the mobile version of sites like Google, Wikipedia, NYT, etc., which makes it easier to use than Opera Mobile. Today the market offered to update it, so I tried it to see what happened, and of course it stopped working once it was updated, so I just reinstalled the old version from the apk. (There is a link to the apk in my comment history if anyone wants it.)
I looked at the battery settings and saw that the biggest battery drain was the OS looking for a cell signal. There is some debate over whether this matters, as obviously there is no radio hardware in the Nook, but it screws up the battery statistics and there must be a process running continuously, so I wanted to get rid of it. I googled it and found you can rename two system apps called phone.apk and telephonyprovider.apk (as I recall), so I did that using ES File Explorer set to allow changing system stuff. That worked, so I thought OK, I will get rid of a couple of other annoying apps I don't need. Unfortunately one turned out to be vital to the system, and the Nook stopped booting. I went through the "eight failed boots" thing and it restored from firmware. All the apps were still on the Android desktop, but the reader was no longer rooted. So I redid the Touch Nooter process, but the screen never "flashed black". After about half an hour I just turned it off, and it booted up fully rooted again. Now it seems back to normal, but I learned a lesson from that.
Of apps on my desktop, aside from those mentioned above I have BBC News, Slate and the Guardian, a train timetable for my country, a Chinese vocab builder, the Google RSS reader, Cool Reader, a couple of weather apps, an offline language dictionary called CC Dict, Google Maps, Gmail, Skype (IM only obviously), an interpreter to play old Infocom text adventures such as Zork, CheckMyTrip, solitaire for my g/f (in black and white, a little challenging) and a notepad app. I also have OS Monitor and Air Droid in the app drawer. There are some others that would have been nice, but though they download from the market they just don't work properly, e.g. the Merriam Webster app.
The battery usage seems fine. It is quicker in the Android OS just because of so many more screen refreshes and much greater CPU usage. Booting into the Nook OS, it doesn't drain at all when left on overnight, so no problems.
All in all it is quite a cool little device, especially once you get the desktop set up to be compatible with the e-ink screen. Mostly I just boot the thing into the Nook OS and use it to read books, but it is nice to have all that functionality there if you ever need it.
EDIT: Turns out BeamReader was just a trial, so I am now using APV PDF Viewer.