I thought long and hard about this very issue before buying my 650. Ultimately I figured I spend a lot of time in front of a computer each day so it is no big deal to use USB to load books onto an ereader. A few of my friends have Kindles and while they find wireless purchasing convenient, they are constantly frustrated by geo-restriction and/or title availability issues - this is a lot easier to get around on a desktop.
Given that ADE requires specific computers to be authorised for DRM content, I do wonder how I would buy books when away from home on holiday etc, though this is not likely to be a problem as I usually travel with a laptop (I find the in-laws don't talk to me when I'm using it) and always have more than a few ebooks queued up to read
(oddly, they have no problem disrupting me when I'm reading
).
For me at least, I'd take touchscreen over wireless any day!