life straw may work if you have fresh water from the source streams bubbling up. not such a good idea for ponds and puddles unless you only need emergency water for a day or two and then can get medical treatment and fresh water. you need to see what micron level they filter. you have a better chance of dying from dehydration due to diarrhea than bad guys (relative to where you live). check out saywer products. they make a .02 kit that filters out all the 99.9999 of the bad viruses; bacteria; protozoa/cysts. not as cheap as the straws; but worth every penny if you really need them.
+100 on the Sawyer filters. The mini is $20 and can be used as a straw amongst other uses. I have the larger Squeeze model and two of the mini's and they all perform great.
I looked at the lifestraw when I shopped around but I'm finding the sawyers hard to beat.
So long as you backflush em with clean water occasionaly they'll last a long time IMHO.
Sawyer filters might not be as fast but they work great. We had a group of 6 people and it only took about 5 mins for us to get everyone a liter of water with 2 filters. If you have multiple bags you can have someone filling bags while the others are squeezing. They are a great light solution and they are what I use when backpacking.
They also come with a straw so if you want to use it like a life straw you can.