The version you see above is for BlackBerry, though functionality should be almost identical between platforms. Like Skyfire of Opera Mini, Bolt performs a good deal of page optimization server-side, meaning that it's fast. In fact, compared to the Bold's stock browser, it's really fast. Rendering accuracy looks about as good as any other WebKit-based mobile browser (Safari, Chrome, S60 default browser) but appears significantly snappier than its competition.
Bolt is in a private beta for now, but you can request an invite here.
J2ME is nearly ubiquitous, barring the obvious iPhone/G1 exceptions. That means Bolt will run fine on your BlackBerry, S60 and Windows Mobile phones, among many others. [CrackBerry]