We have one and found it pretty useless.

Didn't keep the smells away, then again, we were only using it for pooey nappies, and not from newborn as bf baby nappies don't really smell! We saved it for the smellier stage (after she was put onto solids) and thought it was not at all effective.

The cartridges are expensive too. We do the same as Lucy - just use a shopping bag. You can also get scented nappy disposal bags which are really good.

Having said that, we still have it and are going to use it this time round - just to get rid of the cartridge that we have left, and are going to use it from newborn.