Rusty Milholland wrote a review of MSR HyperFlow Microfilter on May 15, 2011
This filter was a dream. Superlight, super fast, not overly bulky. Not the easiest to pump but that doesn't seem like a problem all things considered. Brought it on my AT thru last summer and loved it for the first week, backflushed when recommended, it acted like expected. Then, around week 2, the one way valves blew inside out. I flipped them around, expecting this to be a fluke as I was using the regular backflushing schedule, but it kept happening. Talked to MSR, they sent me a new unit. Used the next one for another week, then it kept happening again. After talking to other thru's, many experienced the same story. Good idea but you gonna have to carry some chemicals (Aquamira is best) anyway cause this thing isn't reliable, so you might as well use them. Or go with the Katadyn Hiker Pro or MSR MiniWorks EX. Both are tried and true and work great for extended trips.
Oh, and read all the positive reviews. "Just used this for the first time..."