Depends on what it lets you do - if you always indend to plug it into a PC to put books on it, swell. if you want to get onto the ineternet and get content with it without a PC it can be useful.

bear in mind any wireless access will suck battery down hard.

I'm still kinda looking at the bookeen. it
seems to be about the lightest one - at 6 oz,
I'd definately take it in a backpack.