I can't speak for the ugliness, but as for the slow to react...
I think the reason it feels sluggish are two reasons: The screen technology has a slow response time. This is alittle difficult to fix, due to the nature of the technology: an electic field turns on or off causing tiny balls to be pulled to the top or bottom of the screen causing light to be reflected/absorbed. Due to the size of these balls (microns), it can take much longer to reorient these balls then the molecules in liquid crystal (nanometers).
The other reason it probably feels sluggish is that the processor is a little slow. Fortunately, amazon has been able to work around this a bit by caching the next few pages. (But if you go backwards it can sometimes take a bit longer to load).
I love my Kindle and can forgive the response times which I'm sure will improve, but on the other hand I agree with John, the software's low quality. It's nowhere near my iPhone in terms of polish, thought or fairly obvious testing.
For me these things bug me:
The keyboard is missing some obvious keys like comma and apostrophe. You have to go into [Sym] for them but you use them all the time when making notes. They're important keys that have been inexplicably relegated to the extra menu.
There's no first letter capitalization when you start typing a note or start a new sentence. Extremely irritating.
The bookmarking system is confusing, inconsistently named and clumsy.
Some things take a silly long time to figure out, like switching between your present page and the chapter list and back. This is mainly because the menu in a book has silly options in it (Turn Wireless Off is the first option? wtf?).
The arrow rocker doesn't work at all well in landscape mode.
Some things require a full screen refresh while others do not (opening a menu doesn't, closing it does). It's just that little bit jarring.
You can't zoom on pictures enough, very irritating for books which have little maps of battles or such like.
I've had it go titwozz more than once when plugging it into my PC. Is it charging, is it not, screen suddenly resets.
Apple wouldn't have let any of that obvious stuff go out of the door, you notice pretty much all of it within the first few days.
Its more the update circuitry that's responsible - it row-scans like an analog TV. Combined with the relatively slow eInk update rate you get the very-large product of a second per frame or so. There is nothing inherent in eInk that demands row-scanning; its just the choice made by the first commercially-available eInk screen.
Patents exist for better eInk displays: http://www.faqs.org/patents/app/20080238894
I look forward to a fast-updating book reader. One day I may even be able to flip through an eBook! Until then they have a long way to go, to reproduce the book-in-hand feel.
I've been using a Kobo since just after release, which has slower page turns than a Kindle. It's annoying for maybe the first hour, then it feels perfectly natural as I hit the "next" button as I'm reaching the bottom line so the screen refresh is occurring as my eyes scan back up to the top of the page.
I think the reason it feels sluggish are two reasons: The screen technology has a slow response time. This is alittle difficult to fix, due to the nature of the technology: an electic field turns on or off causing tiny balls to be pulled to the top or bottom of the screen causing light to be reflected/absorbed. Due to the size of these balls (microns), it can take much longer to reorient these balls then the molecules in liquid crystal (nanometers).
The other reason it probably feels sluggish is that the processor is a little slow. Fortunately, amazon has been able to work around this a bit by caching the next few pages. (But if you go backwards it can sometimes take a bit longer to load).