I'm pretty similar to you in that the 'extras' are really of no concern to me, it's all about just reading a book. Browsing the internet, note taking, audio etc don't matter at all, and the difference between the screens are pretty minimal.
So apart from the biggie of where you are happiest buying your books from, the how it looks & feels in your hand, and how it deals with page turns (plus how much does it flash, is it fast, is there any ghosting) are the main things.
Unfortunately, I can't really help you make your choice, as I'm still undecided until I can get a proper go at using all of them - which is what I think you really need to do before deciding. Though you don't need to be as pedantic as me! If you make a choice you'll probably end up being really happy with whatever one you have chosen, once you've taken the plunge!
Swipe or tap to turn pages - I think I prefer the tap of the Kindle (and you have the option to do either), not sure if you can do both on the Kobo, and I think it's swipe only on the PRS-T1 but with the option to set-it up so you can swipe from either side. Neither the Kobo or the Kindle have physical page turn buttons which I think would be a big miss, and although the PRS-T1 has them, they are at the bottom and not on the side.
The problem is, this is something that you are probably only going to discover your preference for with a bit of use...
Which leads onto how it feels. Being in the UK I've only played with the non-touch Kindle so far, though I liked it. I've only had a very brief look at the Sony and will probably need to go back and make sure it's one running the latest firmware.
I have played about with the Kobo and was impressed with the way it looked, speed, lack of ghosting etc, but it was attached so tightly to the display stand I couldn't get a feel of the quilted back.
As soon as the Kindle Touch is out in the UK, I'll be back round all the shops playing with them all over again.