I like them. Maxi mods are nicer, but the hydors are still pretty darn good. And it's not a good thing to run on a wavemaker.
In my 40 breeder i had a 4, 3 MJ 1200s, a 300 GPH HOB filter, and my skimmer. It was mainly sps, but there was everythign in there.
in my 10 gallon right now, i have a 2, my skimmer, a 100 GPH HOB fuge, and i have 1-2 more 50 GPH powerheads just to keep the bottom clean.....
but of course, i like a LOT of flow.... you could definatly get by with less.