To date there are no Froyo ROMs but there is an actively developed ROM based on 2.1. I've also read that someone is working to port CyanogenMod 6 to the Backflip but I can't say for sure if it's still being worked on or if it every truly was being worked on.
The 2.1 ROM that's being developed has overclocking capabilities as well as JIT which should increase performance. I'll be loading the 2.1 ROM onto my wife's Backflip this weekend since it should help it perform better.
a dev named kernelzilla is working on froyo (CM 6) for the Backflip. it is not available to the general public yet, but i am a alpha tester and i am using it as my daily driver. the only major thing that does not work as of right now is the camera. if you want to see the progress go to Freenode IRC with the channel: #motus
I'm running the 2.1 (J RoDD's preclaire) on a backflip, and it took the phone from brick to brilliant... well that may be a bit much, but the stock 1.5 that comes on the phone outside of the USA is brutal. I had my phone less than a week before i changed it to 2.1.
I'm taking a look at the cyanogen 2.2 port, right now and probably going to forward with it from what i've read so far.