Thanks to all for the info: the 350 sounds a good step up in usability from my 300.
Can you also tell me whether the 350 does any automatic styling of <a> tags found on a page or whether it simply respects the CSS defined in the ePub?
The 300 gives me good control by using the ePub CSS, except for the first link on a page which it automatically highlights in white text on a black background, (maybe this is helpful as it's effectively hovering on the first link), and I'm hoping that the 350 works similarly.
It's not easy to test such things in shops as they naturally don't let you load your own books on!