I've been reading as much about Flock as I've been using, and the popular opinion seems quite mixed. Interestingly enough, the world seems to have wanted something very revolutionary, rather than evolutionary, which is most interesting. Also, the opinions seem to be mostly from Firefox users. In fact, I'm not sure I can find a review by someone that actually uses IE as their primary browser. Well, that's probably not fair...I am sure the folks at Business Week probably had to convince several layers of IT managment to allow them to use something other than IE.
One of the more practical reviews I read was by Dion Hinchcliffe. His review had a more reasonable "I know this is based on Firefox". His ideas are quite good, and frankly the comments on del.icio.us actually would make it interesting to me. Tagging, grouping, and more importantly, suggesting are the parts of del.icio.us that encourage me to share and involve - I'm getting something back. The currency exchange is clear. I add to the collective, and I get back. I'm very willing to be more organized and share with my fellow man if I can leverage the collective intelligence.
If nothing else, Flock has inspired me to dig a little deeper into some technologies I couldn't/didn't value previously. That certainly is a point for Flock. I need to spend more time with del.icio.us this weekend.