I got Firefox (fennec 11.0) up and running with adblock. The good news is adblock does its job. Firefox's tabs and menu system is similar to Dolphin HD on Android, so I am familiar with the interface and like it. Although since it's combined swype, it can make life a little difficult. Rendering is also very quick, at least on par with the stock browser.

The bad news is that the menu system is very sluggish. A tap anywhere takes far too long to register, the menus are inconsistent (some are white, others are gray), and the text does not reflow on zoom even if the option is enabled. It also crashed a couple of times.

I am aware this is at best a beta version, so these kinds of issues are to be expected. But I think I'll stick with the stock browser for now. I will look into editing the hosts file, see if that gets me anywhere.

If anyone is wondering where to get Firefox for the N9, here's my source:

http://romaxa.info/fennec/