It sounds like this game has a few things going for it, one being seamless multiplayer and single player. A lot of how well this turns out depends on the quality of the bot AI, but sometimes it is fun to play on your own when you want to, and I like that you have the same character/attributes/levels accumulating either online or off.
I also like the tighter range of basic combat capabilities for classes. Classes in TF2 are so specialized, from what I understand any of the medic/eng/soldier/spy can pick up and use any weapon in Brink, it is more your character's chosen body type that limits your weapon options.
Regarding the same character between online and offline, I hope it does not mean needing a active internet connection for offline/single player mode. All those systems so far have sucked for me. I put that down to living out side the US for most of the games (ie: we do not exist for the game developers, but they still want our money).
As to the classes, it reminds me more of the older Tribes style games. Will be interesting to hear a review from a old time tribes player on the topic of classes before spending money on this game.