My testers tell me sometimes it works 100% others it doesnt.
Most keyboards have certain lock-out combinations, due to their design (multiple keys sharing the same circuit paths, if you have more than a certain number of hits it will block out the others)
for example: if you have the "UP" cursor key down, it will detect either "RIGHT" or "LEFT" at the same time, but it won't see UP and RIGHT and LEFT.
This is one of the main reasons many games started using the control, alt and shift keys to shoot -- the modifier keys always work and don't block any other keys in the process.