Just got back from a week-long hike on the AT (Ensign Cowall to Pine Grove State Park) using this filter and have a few additional thoughts.
Our group - We had 12 total people in our group and hiked in small groups of 3 or 4. We had a gravity filter, a pump filter, my Sawyer Squeeze filter, and 1 or 2 that used Aqua Mira. As each small group reached a water source, whoever had a filter treated water for their group. I usually ended up filtering 6-8 or so liters each time.
Rubber washer - The rubber washer fits into the filter too loosely and falls out quite easily. Need to either put a spare in the kit or check my local hardware store for a slightly larger one that will stay in place.
Push/Pull Cap - Aiming the stream of water was easy and flow was plenty fast enough to allow me to hold the bag at an angle so that any untreated water dripping off the bag wouldn't accidently fall into the water bottle. I originally thought I might replace this cap, but I'll keep it like it is for now.
Extra Scoop Needed - Several of the water sources we encountered were no more than 2-3 inches deep. This made filling the water bag more difficult. I forgot to bring a scoop and had to use someone else's cup to fill the water bag one cup at a time. This was slow and tedious. I think I'll probably cut the top off a plastic water bottle and carry a .5 liter scoop with this kit.
2 Liter Bag - On the second morning of our hike, just North of PenMar. I filtered several liters of water and filled the provided 2 liter bag to top off bottles after the climb up to Deer Lick Shelter. Another hiker fastened it under the lid of his pack. Halfway up the hill, the bag fell from the pack landing on a rock and burst. No more bag. Fortunately, I had an extra 2 liter Platypus bag with me.
Capacity - The high temperatures in Southern PA last week ranged from 84 to 93 degrees. We went through alot of water! I was able filter water for myself and 2-3 others easily and quickly (except for filling the water bag).
Cleaning Syringe - I carried the syringe because I was unsure how long it would take for the filter to become partially clogged and slow. Never used it. The flow from the filter never varied one bit after filtering dozens of liters during the entire week. I did, however thoroughly backflush the filter with tap water upon my return home. I'm convinced that the syringe can stay at home for weekend trips.