Speaking as one of those sending out quite a bit of info from the conference keynotes, I think that your observations are accurate. There was a lot of information going out in real time (and 140 or fewer characters at a time). I didn't re-send some bits as others were faster than I was. I sent out some news that had already been reported because I wanted to lock it in a little more. Sadly, I have to agree about the Dell speaker. I feel for the presenter and hope they find a better way to handle that in the future.
Of course, one of the great things that I got out of the Twitter feeds this year was the opportunity to meet new people and to keep up with what was going on in other sessions. I got some good info from @sqlbelle from some of the sessions she attended and resolved to get the slides/code ASAP from those and review those sessions earlier once I get the DVD. I was greatly amused that Paul Randall was able to heckle Buck Woody remotely through people using Twitter. I enjoyed meeting the Bingo players, though I wish there were more of them.
As you noted, Twitter can definitely be used for more than pics of meals and notes about "going for coffee" (which seemed to be available ~ every 1/2 block in Seattle). I've followed others attending conferences and they'll typically post some of the great moments from conferences I can't attend. It's not like being there, but I can benefit from those who are.
I'll also add in one last bit and say that it's great to finally put names to faces, but it's really, really hard to match up twitter names to real names. I still have a hard time matching many of the more creative twitter handles to their owners.
If I get to attend next year, I'll be joining in the stream again (to the chagrin of my co-workers) and if I can't attend, I'll be joining people like Jorge (@sqlchicken) in participating remotely.