I didn't fully test my Polar with Renoise with the new 3.1.0.0 update, but I read in the Manual about a fixed static buffer thing.
apart from that it worked great for me. I use the hardware outputs on the Polar instead of the USB for this.
We are now rehearsing for new live material, when I take it back to the studio I will discuss functionallity further.
(for now we just hooked up the polar with the good old MIDI cables).