Probably just because you don't have the pages cached yet, I compared chrome to Waterfox for opening up BLF pages and I couldn't find any real difference
That's probably it. Honestly though, the scrolling feels nicer, which isn't a lot, but when web browsing, actually seems to make a difference. It's less jerky than it was on Chrome. I'm also noticing significant memory usage decreases, which is nice. :P
If it was Chrome doing the weird switching thing, Waterfox may be the way to go, but I guess we still don't know for sure what is causing the switching.\
Edit:
Can't seem to use gmail... I'll probably figure it out though.