I had a ReefKeeperlite for a while. it was a good little controller, but was only expandable to 4 modules. I upgraded to the Reefkeeper elite and am much happier.
Agreed with subielover. And I would imagine Rick will comment the same. I've had RKLs, RKEs, and an Apex. The Apex is a much, much better value (if you want anything more than basic control) and has better support than the RKLs and RKEs. However, my RKE was still a good unit and the RKLs can't be beat for the price, they're just not very expandable as Lindsey pointed out.