I completely swtiched to Ableton a few months back. Previously I was working in Cubase, but now when I am more familiar with Ableton I never look back.
You can do everything like in other DAWs, but to me it seems to be more "musical" in terms of workflow.. Work with MIDI is bit weak, but hopefully they will improve it one day.
Overall, I dont think it will take you too much time to learn it.
As for the Bitstream, yeah, I've got one and it is great,. Solid construction, no cheap plastic. It has some nice features, like built-in Arp and LFO, ribbon pad, X/Y joypad,. Crossfader seems to be bit flimsy, but I am not using it too often. It can emulate Mackie Control, you can easily edit all parametrs in Bitstream editor and waveidea is updating firmware reguilarly so they are adding new interesting features...