The Sonuus B2M isn't useful live for normal or fast playing. They've nailed the latency issue with super fast tracking. Velocity tracking seems excellent. However, the pitch tracking is extremely flakey. It will pick wrong notes frequently, and more annoying it has serious ghost/retrigger issues where you'll play a single note but it will trigger a few NOTE ON/OFF sequences quickly. The wrong notes I could probably learn to deal with, but when it sends 3 NOTE ON events for a single note it screws up envelopes and what not.
Note you can hear all of these issues in the YouTube video linked here:
http://www.youtube.com/watch?v=Gc8FbTKqgfs Wrong notes, doubled/trippled notes, all of it.
But they've nailed the latency. It's absolutely playable in that regard.
I was having some good success using the B2M to control effects with Velocity and Note data. I'd set my software, Plogue Bidule as my VST host, and could set a keyboard split (which ghost/retriggers don't affect, though grossly wrong notes would) from the B2M output to do channel switching and toggle effects in real-time, or use Velocity data to control VST parameters as the Velocity output seemed very solid and responsive, though sometimes a little hot so I'd have to use a velocity scaler to keep too many of the notes from peaking at 127.
But using it to trigger VST synth like Massive for awesome electro-dance bass wasn't working at all for me. Way too glitchy.
Related to all of my adventures, free VST audio-to-synth apps like FrettedSynth GuitarSynSE was much, Much, MUCH more usable as it tracks pitch directly, thus no MIDI necessary. It has issues tracking latency properly, so I'd feed it a heavily gated and squashed/controlled input. But the tracking and sounds are excellent, as is latency. Korg Legacy MS-20 tracks pitch as well, though I found that VST overall to be less useful due to the sounds it produces.