What's wrong with this DC motor controllers?

Most DC motor controllers I've seen, such as those from Polulu, cost almost 10 times the cost of this one:
http://www.ebay.com/itm/PWM-DC-Motor-Speed-Control-Speed-Switches-Pulse-Width-Modulation-High-Quality/390580920598?rt=nc.

Is there something wrong with this one?

dptdpt:
Is there something wrong with this one?

Apart from that awful pink flowery ebay page?

As far as I can see, it doesn't give any specs about voltage and current, so you don't really know what to compare it to.

Judging by those 2 huge heatsinks, it's an older inefficient technology, whereas Pololu's are all afaik more modern more efficient devices. Pololu's equivalent of my Motomama which is a 298 and as big as a bar of soap, is the size of a US quarter.

There's not enough information on that site, you cannot tell if its any good or even if
its single-direction or an H-bridge.

At the very least you need to know what device(s) a controller uses then you can
check the datasheet (even then the supplied part could be a knock-off).