As I've just discovered, Blackberry and WAP is free on the unlimited plan, but Mobile Web is not (this much is clear from their website).

I've been using with username o2wap and password = "password" for opera mini. It only works intermittently however. When APN was mobilewed - it worked all the time. So on the basis that when I don't have an APN specified, opera mini does not work at all, I'm inclined to think that the APN means opera mini works on WAP (which is free). However, it's not great in that it opera mini doesn't always work. Would be curious to see if anyone else has the same problem.