I have a Katadyn Hiker filter and am happy with it. But if I were going to use one of those straw filters, I would take a piece of coffee filter and a rubber band and put it over the pickup end of the filter to act as a pre-filter to keep big debris out of it and have it work longer before it clogs up.

From the LifeStraw FAQs:

Q: Does LifeStraw® personal remove parasites like cryptosporidium and giardia?

A: No, the present version does not filter any parasites.

I've got a couple of the Frontier Filter Straws in various kits as back-up. They claim down to 2 microns, and purportedly they grab crypto and giardia. I've not personally tested.

Edit: Found that McNett/Aquamira now has a slightly larger "big brother" to the Frontier Straw — the Aquamira Frontier Pro. Attaches to tubes, bottles, etc. and has pre-filter. 1-1/4 in. x 5-1/2 in. Inexpensive.

I found this about the Pre Mac SWP.

http://chppm-www.apgea.army.mil/WPD/WPDShare/177/AddInfo_PreMac_SWP.pdf

Apparently, according to this report, it is not effective for Giardia or Chryptosporidium.

Here is a good source of info for filters/purifiers, I think it may have been posted here before.

http://usachppm.apgea.army.mil/WPD/CompareDevices.aspx

I guess for now I'll stick with my MSR and Chlorine Dioxide tabs.

Thanks for the input all.

Blitz