Naw!

When I got my Clie T625 (320x320) it was a revalation and the first time reading on a handheld format was practical to my mind.

Now I have a Loox (640x480), I can't say that it is much better than the Clie but the extra screen size does give me a few more words.

I find it best to reverse the screen so that I get white text on a black background, much less tiring but the hi-res is SO much easier to read.

Of course, it also matters what reader you are using. I have found that the MS reader is nowhere near as good as MobiBook or eReader.

Full screen can also help because it turns off distracting features.