Having never been hit with Guardia, but having read some accounts of people that have had it, it may not attack you when you drink the water, but it sounds like no fun to go through a week or more after you drank the water.

I will continue to boil or filter my water. The fact that I enjoy primitive camping in remote areas, and that I have always made my water safe to drink supports (in my mind) the idea that the small amount of time and effort it takes to boil the water is well worth it.

Boiling is easy and with any fire be it a wood stove, tin can hobo stove or a small campfire, fuel is not a big deal.