@Slo - I retrofitted my ULA gravity filter with a Sawyer. The great thing about the sawyer is that it can be back flushed if it starts to get slow. I love my Sawyer filter.
I used this filter on a group trip to the BWCA last June, and we ran 30 or 40 gallons of lake water through it. It slowed down about 20 gallons in, and I just back flushed it in the field to get it back to its normal flow rate. What's really impressive is when you get home and back flush it under city water pressure. There was a lot of gunk hiding in there!