The pages of discussion here have been very good.  I have one or two questions/comments.
If anybody has one of these straws that do filtration - could you actually give us a field test report.  I'd really like to know how easy it is to suck water thru the straw.  For example, if I place the end of the straw in a puddle of water (cloudy water) and suck on the other end - how fast does water come through?
I have generally used filtration, and especially like Katadyn.  The main drawback is that the water needs to have dirt/mud removed first or the pores in the filter will clog quickly.
Iodine tabs and other tabs are probably fine.  In a pinch if I was desperate ... bleach too.  It's just that the water tastes bad afterwards.  You need some discipline to drink a lot of that stuff.
There's nothing wrong with good old fashioned boiling.  Can't argue with that.  I keep seeing different numbers for how long the water needs to be at a rolling boil.  
Pete2