This is the sort of preorder bonus we like to see. You can keep your costumes and your specialist weapons, Frozenbyte are offering you instant access to the multiplayer beta for Trine 2 and all you have to do is preorder it through Steam. That'll set you back £11.99, but initial reaction seems to be that that price is well worth it.
The Steam page also gives a vague mention of a 'December 2011' release date, the most concrete information we've been given so far.
If you're not interested in the beta and would feel more comfortable with the console version of the game, don't worry. You're not really missing out. Frozenbyte developer fb_joel clarifies:
"The graphics are marginally better on PC, and of course you get more display resolution, but other than that the consoles are very good and on-par with the PC version. So you should buy the game for the platform that you feel most comfortable with."
Earlier he'd said that every version of the game should be released within 24 hours of each other, but with the way digital managment is handled on consoles this could be subject to change.
December can't come quick enough.