I used and love the stock browser, but I'm now trying Dolphin HD. With the way I have it setup, it's similar to the stock browser(which I'm use to), but with more options. Btw, I don't think Firefox supports flash.
I use both stock and firefox because i use firefox on my laptop at home and i love the sync feature.
Only downside is no flash support, but imo once they support flash on firefox, with all the features and cool add-ons like 'close browser' and 'pdf maker'...it will be my number one browser for sure.
Stock and Opera Mini. I only use Opera Mini when I need to go to a site that keeps closing the stock browser. I don't know why, but there are a few sites that cause the stock browser to just close and return me to the home screen with no warning or anything.
I've tried all of the Dolphin browsers and they don't really do much different from the stock browser and they seem to be a little slower in my experience. So 95% of the time I'm using the stock browser and the other 5% I'm using Opera.
I have been using dolphin hd for a long time now. I have to say, the stock browser on the tbolt is pretty solid though. Also, I need to go back and try firefox now that it is in a final release stage. The beta was slow and crappy, but everything ive read seems to have shown that its doing a solid job now too.
I use Dolphin mainly because I have the option to make gestures for page to the top, an page to the bottom plus upon exit it will clear history/cache/cookies for me.
I do use Opera for being able to type and add attachments in my POP3 email none of the other browsers do this, and I have used the main ones OEM,Dolphin,Skyfire. Sidenote I havent use firefox so I dont know if that will all typing in POP3 mail