We got this nappy wrapper free, but even if we had to pay money for it, it'd be worth it. It's easy to use, cartridges are easy to change and it contains the stinky nappy smell brilliantly. Have only found one place to buy replacement cartridges however.
My only gripe - now our daughter is getting older and wearing bigger nappies, we find we have to change the bag every week, but as it's not difficult, it's not a problem. One cartridge lasts us about three weeks now, but they're only £10 for 3, so it's not bad.