I've been wondering the same thing. For those of you that don't know what this means, the user agent feature allows you to load a website's non-mobile page from the get-go.
OP, I installed Opera Mini Browser and it seems like it loads the non-mobile sites from the start. Maybe I just haven't visited any that have mobile pages, but it seems like that one works.
If anyone can figure out how to get others to work, I'm all ears. Until the jailbreak is out and I can install User Agent Faker, I guess we're stuck with this.
*edit* Dammit. I just tried Opera with a site that has a known mobile site and that's what loaded. This sucks!