I pretty much use Firefox as my standard browser, it starts relatively quick(3-7 seconds), it has some add-ons already(and more to come, I hope) and it does support flash, after enabling. And with Adblockplus installed it barely slows down, sure sometimes it won't react immediately but I still like it. Plus tabs spells awesomeness.

@Rushmore: See here for instructions to enable flash, works perfect for me: http://www.nokiaphoneblog.com/?p=2945