One trick i learnt (if your an ableton user) is to put warp markers on each transient in the loop (which does take a lot of time) then use the slice to midi track option, on the drop down menu select the warp marker option, then slice... The good points of doing things this way are that if you wanted to slow the beat down it won't loose quality in the hits when they become stretched. However as Al Kent said, if its a person who played those drums and you quantise everything, you will loose that human "swing" and that is not a good thing..