I went with the ULA Amigo which uses a Hiker Pro filter. I had thought about making my own after I read this thread on a DIY one. But after I priced the replacement filter cartridge ($40) and the rest of the pieces I needed, it just made more sense to buy the Amigo. It just came last week and I've only tested it in the bath tub. I wasn't sure if I would like the bag as it is made out of one big flat piece of 1.9 oz rip stop. But it actually fills up pretty easy in only a couple of inches of water.

I like the idea of double Platy set up because you could always use the dirty bag in a pinch by just sterlizing it out with some Aqua Mira or similar chemicals. That way you always have a back up bladder and even the ability to use both at the same time if warranted.