Megasquirt works fairly well. I was one of the members in the group buy for the first 100 board spins we had made. (After everyone left the EFI-332 board). I converted a carbureted Buell to EFI, replaced a 32 bit Suzuki Hayabusa ECU with Megasquirt, and Fuel injected an NHRA Prostock Harley Davidson that was previously running carbs and having trouble with vibration induced fuel delivery issues.
That said, it's not as easy as just plugging something in. Also having my own dyno for tuning went a long way towards speeding set up. However, if you can crimp and solder and do electrical test and troubleshooting, MS is a great way to get into EFI building and converting.