I agree, it was one of the best things I ever bought for DS! I had one called Diaper Nanny which apparently you can't buy the cartridges for anymore My only recommendation is that you check reviews and make sure that they aren't heavy on the plastic consumption.
Some like the Tommee Tippee ones put a couple of twists in between each nappy. To me that seems just as wasteful as tying a knot in the bag (using extra plastic). And apparently some brands don't hold many at all, although that didn't concern me as I always emptied it at the end of the day. My Diaper Nanny was just a brilliant smell enclosing system that was hygienic and easy to use. I would definitely get one again if I could.