Works fine. But you have to schedule all your timers manually on the maggie and again with auto-tune timers on the H20, and you can't watch anything else while you're recording, and none of your recordings will be in HD. The maggie doesn't have an integrated guide and blaster to control the H20.
Realize that there are no lease fees for DirecTV DVRs, only the $6 DVR access fee which applies to your whole account. 20 cents per day is a small price to pay to avoid the kludgey setup above. With a DirecTV DVR, you can simultaneously record 2 programs in full HD while playing back a third. The guide and recording management is fully integrated. The whole experience is much, much better.