thanks natch for telling us about your experience. very interesting to compare. i've also been really pleased with the reaction time and the ergonomy, which seems to be your experience as well.
my eyes are quite sensitive to light too and i really don't like reading on a backlit screen, so i never expected to use the lights at all, but then one night i was reading in bed and it was freezing, and i wanted to put my head under the quilt, so i pulled the reader in with me and read using the frontlight. amazingly enough i found it reasonably comfortable (i still prefer reading by ambiant light but i could easily imagine doing it again). plus you can regress to childhood nights of reading in bed with a flashlight when you were supposed to be sleeping.
i've not had any trouble with the bookmarks ; they work fine for me, and i've never gotten the notes screen instead that i can remember. but i usually quite naturally use my fingernail on the touch screen, which definitely gives more precision. and probably avoids fingerprints as well, since i've not had a problem with that either.
i've been using the notes a lot, to mark words i don't know or errors in the text to correct, and i really love that feature.
i would not be suprised if the people who are the happiest with the 700 are the ones who previously used an 1150 (or similar) and got really used to the features it proposes (like touchscreen, note-taking, search, and even lit screen, for many...), whereas people using the 505 or cybook might be less interested in those features. the use for research etc. is a good point but i think it's maybe only a partial answer ; i don't do research but i use the notes to mark errors in the text or to note a word i would like to remember or citation that i like, which i already did using the 1150.
overall i'm very happy with the 700 despite the somewhat inferior screen (although i hardly notice it now). i think sony is definitely on the right track with the 700, although it's not quite the perfect liseuse *yet*.