I have one, it works great. The best part is that it is so light weight followed by the ability to pack the big bladder and use it for water storage too. The only negative's are that it won't do a volume of water quickly and it takes some effort. If you need a gallon you are going to be there for awhile. Your hands will also get wet using it which may not seem like much until it is about 20 degrees and the water is just above freezing.
All in all, it is cheap enough to have one in every pack and the weight savings outweigh the pain of actually using it.