I haven't personally used that one.
I've used the Marina c10 and I like them a lot, but you have to acclimate the heater longer then they say on the box to be sure it will heat correctly according to reviews i've read about people complaining about it. I haven't had one let the water drop below 76, ever. And that happened in a 5 gallon which it was not recommended for. They keep my small tanks at 78 pretty reliably.
The other I used is the zoo med round pad thing. I must have gotten a defective one or something, because it had my fish water up in the 90s before I ripped the plug out of the wall and the heater out of the tank. Needless to say I've never tried that one again. Some members have been using this one without any problems though, and like it.
I want to try the Hagen Elite Submersible heater (25 watt) next if I need to replace one of my heaters. They are small adjustable heaters within a certain range. They are small, and my local pet store carries them now.
Sorry to post about a bunch of heaters you didn't get, just thought I would share the info. You should post here when you test yours out.
We should have a product reviews section of the forum. :D