I just switched to Revolution from Frontline for my pom mix, as he was still having flea issues. It seems to work fine, and it's nice to have to remember only one time for both flea and heartworm protection. It does seem to make him a little itchy, though.
I trust Revolution to protect my dogs against heartworms and other threats that may make them sick. I've used it for a long time and have never had any problems. VetDepot carries it at the best price I've found.