I took a SteriPen for one trip a few years ago and then returned it to REI. In fact, after one day, I put the thing back in the pack and used my backup Katadyn MicroPur tablets. The switch was too stiff for my fingers and, once I got it on, the UV lamp cycles kept aborting before they were finished. And that was with my electrical engineer son at streamside with me carefully reading the directions!

If you must use it, be sure to take extra batteries and a backup method of some sort!

By the time you add up the weight of the SteriPen, extra batteries and the required wide-mouth water bottle, you're far better off to take a Sawyer Squeeze.