I've tried Sailfish default browser and like many, I find it a little slow and quirky.
Firefox fared a little better, but has recently started causing some weird behaviour. It will freeze momentarily and disable the Ghostery plugin on it's own, the screen will also become unresponsive with certain swipes and when I minimise Firefox I find the apps running in the background on my homescreen (clock and calendar) have shut down.
Started using Opera yesterday and found that pretty stable and very quick. It was my browser of choice on N900 and I'm beginning to like it on Sailfish.