Another cool thing about Fire is that you speak from either English, Spanish, Italian, French, or German, and that the other person speaks one of those, and if the two are different, it will translate between the two languages for me. Granted, everyone I talk to speaks English as their native language, so for me it's useless. Still, a cool feature.
The things that have me using Proteus right now are the somewhat more frequent update, cleaner GUI, and subgroups. Groups are nice, but subgroups are much better. Being able to take a guy named "Steve" who also uses ICQ, MSN, AIM, and Yahoo and put all of his contacts in a subgroup named "Steve", collapse it, and then have the status of Steve show next to the folder as if the folder were a contact is amazingly useful (I'm adding an attachment to show what I mean). It cleans up the GUI a heck of a lot. Fire doesn't have subgroups, and so it's way too cluttered for me.