I’m really digging flock, and not because of all the web 2.0 snazzyness. I honestly couldn’t give a damn about that. The part the makes me warm and fuzzy is just how much faster it is than Firefox on OSX. I’m not sure I’d use flock on Linux or Windows (I might change my mind later after using it for more than a weekend)
The other feature I like over camino and safari is that is supports most of the extensions I used to use in Firefox. Camino had some hacks, but they weren’t the same. Safari had some non-free plugins that slowed it down a bit. Flock just feels like firefox but FASTER.
As far as the web 2.0 features. I would love gallery2 integration, because I dont use flickr much. Delicious integration has made updating del.icio.us easier, the blogging tool is *ok*, but I still prefer dashblog at this point.  Although this has a cool tagging feature. The search box is interesting, but I’m still getting used to it.
Anyways, thanks to the flock team folks I finally have a decent browser on the mac.