[Aurinko]

I have had my Sony DPT-S1 for five months now, here are my thoughts.

What I was most worried about was the input lag of the stylus, i.e. the delay between making physical contact with the screen and pixels appearing on the screen.

As opined by numerous people in this thread and elsewhere, the input lag is negligible. There is a noticeable delay but it doesn't negatively affect my handwriting any more than the little quirks one must tolerate when working with real (graphite and ink) pencils and pens.

Another important aspect was the display quality. I had done what research one could on the Internet and it looked good, but I wasn't sure until I'd get to perform hands-on closer inspection.

No surprises here; the display is indeed great. You can distinguish the pixels from close range, but antialiasing, 16 levels of gray and 150 ppi easily suffice to provide a soft, yet sharp reading experience. I have some PDF's on which the text is still readable when fitting nine pages on the screen, but in most cases this is breaking the limit of the pixel density. I can easily read most single-column PDF's in a four-page view.

Build quality is superb. I think I have a knack for determining the build quality of a device in a matter of seconds by touching and feeling it, and in the long term I find that the initial impression was almost always indicative of the overall sturdiness and durability of the device.

Physically, Sony DPT-S1 has a very satisfactory feel to it. I have dropped it on the floor without the cover on, a cat has jumped on it and walked over its exposed screen, I have read outside in light rain, it has traveled with me (in my backpack) in -15 to +30 deg Celsius (5-86 deg F), and I have deliberately exerted pressure on and tested the flexibility of the frame. Apart from litter and dust particles accumulating in the ~0.4 mm seams between the display and the display frame, and the frame and the back plate, it still looks and feels mint.

Sounds good so far, and indeed these are all areas that commendable engineering went into, which helps to justify the premium price.

Then on to the negatives...

The user interface is - although mostly functional in its minimalism - severely lacking. There are so many functions absent that would make using the device easier and faster. I'm not going to list them here - suffice to say that when working with multiple PDF's the experience feels like constantly having to jump through hoops and taking detours instead of the shortest path. So much room for improvement in this area, but I suspect the lack of effort in it is somewhat related to my next gripe about the DPT-S1...

The hardware and software "kind of" do their job, but nothing to write home about. Since I'm not sure which is the bigger culprit, I've lumped them together as they are so intertwined in delivering performance and user experience.

While my fear of the stylus lag was in vain, in regular use I feel that lag is always present, even if just lurking while things run smoothly, waiting to rise to surface. Sometimes the device simply chokes and loads a page (plain text or light graphics) for several seconds, doesn't respond to touch at all, doesn't SEEM TO respond but then flips several pages in quick succession because the commands got queued, sometimes it does things by its own will (static electricity?), PDF's can take ages to load to the point where switching between multiple files becomes such a strenuous act I find myself trying to avoid it more than I should, whether zooming works is often flipping a coin, etc.. Zooming on handwritten documents also gradually slows down to a crawl as they accumulate information (writing speed is still mostly fine, but rendering the curves typically starts lagging behind more). In short; too much waiting around. When I'm reading paper books my speed is limited by my dexterity, while on the Sony my speed is limited by the UI and the OS/CPU/memory.

Worth noting is that the drawing speed of the display is not the problem. The display technology has its limitations but I'm totally fine with what it can do. What I find unacceptable is (in this era of low-cost electronics) the system lagging behind the slow display.

The calibration of the stylus isn't quite perfect. Essentially you can adjust the angle that the stylus must be held in to cause it to activate a point in the display that the stylus tip touches. The sensor is so deep beneath the display that a fair amount of programmatic compensation must be made in order to align the point that visually appears on the [near] surface with the physical tip. No problem conceptually, except that since I am not a CNC machine, the angle of the stylus varies depending on the position and angles of my palm etc., which means I have to manually do extra compensation by taking the calibration into account and adjusting my physical movements accordingly, which does feel unnatural but is something I have mostly been able to adapt to.

The choice of Android 2.2.1 puzzles me. As far as I know, the whole essence of Android is being a flexible and somewhat extendable general purpose platform - things that the DPT-S1 clearly is not, as Sony has been very reserved about even marketing the device to individuals, targeting institutions and companies instead. This makes me wonder why they didn't choose to build their own optimized proprietary operating system instead. Perhaps the SoC they used was available for low cost, maybe it had already been extensively tested with Android, or the familiarity with Android from the smartphone/tablet segment made it the easy choice and cutting development costs was deemed necessary for profitability. What ever the reasoning behind those choices, the end result is that the DPT-S1 feels like a beta. I think this is in part (besides high development costs involved with developing cutting-edge technology) why Sony didn't roll it out as a consumer device and decided to carefully "field-test" the product by marketing it to institutions and companies with which they could maintain a closer and more private and direct line of communication and be motivated to respond more swiftly to feedback. A premium price beta e-reader would also have been difficult to market to consumers and prone to fail, possibly leaving a stain on Sony's reputation.

All that said, am I happy with the purchase? Yes, because the DPT-S1 is an asset to my toolset that I didn't know I needed until I got one. Now I am carrying a small library with me everywhere I go, that weighs 358 grams and slips smoothly into and travels unnoticeably in my backpack's 14" laptop back pocket. As a result I have done a lot more reading than before and spared a lot of paper. While studying I can write markings and highlight text in books without brutalizing them (which is the reason pen(cil)s are not allowed near my paper books). If I need to sketch something, afterwards I can "trash" the whole page in a flash without producing waste. Now if I know I'm going away for a few days, I leave my laptop home and take the DTP-S1 with me.

I have acquired a fair number of gadgets and novelty items that turned out useless or uninteresting in long term, and Sony DPT-S1 does not belong in that category. I'm sure it will be traveling with me until it dies or gets replaced. In the meantime I will be keeping an eye and ear out for similar devices with better specs.