I tried the first beta, and then gave up, but came back for this one, and the improvements are noticeable. It is technically faster than the first beta by quite a bit, but that's like saying syrup flows faster along a flat surface than it does uphill. It's painfully slow compared to the stock browser, and it dies when switching from portrait to landscape. I am running it on an OG Droid, and they admit to problems, so I won't judge it until they release the final.
Now for the good parts. The UI is tons better, and all around just feels like a complete product. Having sync built in is nice, since that's the only reason I would use this over stock. The storage space requirement was also much more reasonable, and interestingly when I moved it to SD it only took up around 140KB of space on internal storage. But anyway, I can say this is a solid step in the right direction, and I look forward to the final product.
Parting words: Considering Mozilla is a non-profit charitable organization run by volunteers, I'm not going to tear apart their products when they don't work 100%. Just a thought...