I like some of the features but there's one thing that always pisses me off - tabbing isn't optimized. Looks like it only uses 2 connections for all tabs, rendering isn't done until WAY past TTFB (time to first byte) and tabs don't load at the same time.
I've had times where I stopped one tab before others started to load and they stopped loading as well. Very buggy.
I'm using it some of the time just because FF3 is still a pig on memory.