Things that speedup loads:
use innodb tables (isam and myisam are outdated anyway)
when using innodb tables yoiu can use a transaction to further speed up the load operation and also to make sure that an aborted load operation does not f*ck up your data.
About the speed itself: remember that if you insert 500k records in two minutes, thats 500000/120=4166 records/second. That's quite fast already.