I would say posting on MobileRead is fairly social.
[just deleted a rather large discourse on TV being a social activity since it sounded fairly off topic, personal and made my home life sound rather, uh, strange (TV habits of girlfriend being completely out of context--I know, sounds intriguing huh? Trust me, it really isn't)]
Anyway, keeping on topic for the thread...
I can completely sympathize with what you say, tcv. The only difference being the main topic of reading. I plow through projects, play games, and so on only to temporarily abandon each if they are not completed before my interest fades. On the other hand, I have always been a bookworm from an early age, not to mention almost constantly reading if my immediate attention is not required. Cereal boxes anyone? I'm the only technology geek I know that actually reads the manual (well, maybe not first, but eventually--I even read the Sony Reader manual front to back). Basically, if a book isn't handy, and I've got the opportunity, consider it read.
Now, I will say that having the Reader has made reading books much more convenient and judging by consumption over the last month-and-a-half, much more productive. I would say that even for an on and off reader, the device would allow you to do more reading when you are in the mood, and keep your place when you're taking a break. I suspect if the price was lower, it would almost be a no-brainer for you, but as has been mentioned above, given time, I'm sure you will work out what is best for you.