I bought the Trailshot yesterday. I was put off by the price of the gravity kit, though. However, I returned the Trailshot today, as it left a chemical taste in the water, even after putting 6 liters through it. Tried backflushing, etc. but still no good. I gather from the reviews that others have had this problem, but certainly not everyone. I'm guessing that MSR uses some kind of solution to sanitize them during manufacture, and some get too much, or too strong a solution. Or maybe some people notice it and some don't. There are a few other things about it that I didn't care for as well. The inlet tube is too short and lacks a float on the end (both things I could fix myself), and the outlet is awkward for filling a bottle. I think it's different on the gravity version.

I may try the Sawyer mini. Filling the bag could be a pain, though. Apparently they let kids design these things (grumpy old guy attitude.)