I took an Adventurer Opti on a trip to Brazil - using it for all water consumed during the week. I used it in classes of water and in a 1 liter Nalgene wide-mouth bottle I brought along. I found it easy to use and didn't have any intestinal problems - which seems to happen all too often when I travel internationally.

My only comment relates to the button you push to activate it. I found that button to be harder to push than I thought it should be. It always worked, but it seemed somewhat finicky.

I have not used it in the outdoors.