It is not just Firefox 3 betas these days, Opera Mini 4.1 just came out in beta. ReadWriteWeb’s got an overview that you might want to check out, otherwise just nab the beta and give it a go.
I had Opera Mini on my mobile phone for a while, but it never really worked nor loaded as fast as the native web browser, although it did handle traditional web pages better. Still, who wants to surf all grown up websites on a small mobile phone screen? We’re not in Japan, every phone isn’t a smartphone… I just might give it a go anyway, we’ll see.
