One thing to keep in mind is that pump ratings are rather variable. Some 2 HP pumps are larger than others. I suspect that a 2 HP pump that plugs into a standard outlet is not going to be nearly as large as the 2 HP full rated pumps that many of us are more familiar with. The number that really matters is the brake HP, which is the rated HP times the service factor (SF). SF varies from pump to pump, so only knowing the listed HP doesn't tell you all that much.
Even with all that, it probably is too large a pump on high speed. But it is much more reasonable on low speed. kmb997 would save electricity with a smaller pump, but with a two speed that isn't nearly as big an issue as it would be with a single speed pump. Having a two speed pump helps dramatically in almost every situation. Low speed is good for filtering while saving electricity and high speed is still available for vacuuming and other special occasions. Getting a cleaning robot doesn't automatically mean that there will never be a need for manual vacuuming or some other situation which calls for high speed.
