I'm with asmrz. If you have ever had giardia, you will filter your water. I was a tough guy and lived with giardia for many years before I realized the long term effects on my intestines was unacceptable.
I wrote a forum post many years ago about a giardia episode, but it must have been flushed away by some SP forum cleanse. Wonder if Matt could find it in some archive for reposting.
Funny thing about giardia, all the people I know who have had it are very prolific hikers who drank from springs and clear streams.