I got my Cool-ER in October last year and despite a few initial problems I now wouldn't be without it.
I use the latest firmware, and have had no crashes/lockups or problems since installing it.
It Does work with Adobe DRM, and I purchase my books from Whsmith in the UK, or waterstones all in DRM epub.
I like that it's able to read a variety of formats, and the screen is great. Would be nice to have the nicer print fonts like the sony / kindle but thats a minor gripe.
It fits my needs well - I tried a sony PRS 300 last night and thought it had way too many buttons and seemed a bit unwieldy; likewise the qwerty on a kindle would bug me. The cooler is a nice clean design, and the case I got for it adds a nice soft feel.
I agree with Amy about the buttons - if you actualy press just the button they're quite easy to push - it's the case that is hard!
As for build quality - well, the plastic (back cover) on mine scratched quite easily, but now I have a case, and the printing on the d pad is wearing off, but I take that as a sign it's been well used! Yeah, the plastic is creaky, but now more than any device that is plastic!
In the UK I've seen a few of these about. Never seen a Kindle, and a couple of Sonys but seems to me that the average Joe in the street has never heard of an e-book - Heck, most store assistants haven't a clue about them either even though they're on the shelves.
I am tempted to get another device soon, but I don't think there's anything on the market at present that will justify the outlay with any new features that i'd use.