I have used one in each corner of my 55 gallon for over two years. They give out regularly, especially if you don't keep them clean. They're so cheap though I just consider them a throw away pump. The model I use goes on sale regularly at Foster and Smith for 11.99 so whenever I'm ordering other pet supplies I'll get a couple when they go on sale just to have as back up. I get anywhere from 3 - 6 months out of a powersweep. I haven't done the math to see how many years at this pace would pay for a wavemaker.
Their lack of dependability drives me nuts, but the way my tank is plumbed and the acrylic overhang limits my choices to try and get some non laminar flow. Right now I'm trying a Maxijet with a Hydor rotating flow thing in one corner to see if I like the flow as well as the Powersweep.
I have some Seriatopora right in front of one tht has grown a reallly pretty shape with the alternating current. I really like the wave motion of the corals in the tank, too.
Cathy