I spent 7 days last year in the backcounty of Yellowstone and the only water I had was from the nearest river. I used two types of water purifiers...both by Katydyn and never had a moment's problem. The water does taste of iodine but it's a very simple system to use.

I think someone has already posted a link to the Katydyn Exstream but we used the Katydyn Base Camp model once we made camp each night as well. I like to carry some sort of flavored drink powder to add to cover the iodine taste but I understand that that may not always be possible.