I decided to take a steri-pen for day use when needed, and utilize a base camp for my evening fill-ups.  I like the handiness of the steripen.  I saw the same problem as PineKnot will shut off it pull it to far out of water.  But other then that it worked peachy!  The + for the base camp is the filter has a charcoal filter system in it, so the taste is second to none.  Also filters out the "big" stuff.  So although the Steripens work to give you safe water, they do not filter out any particulates.  I also have a Hiker Pro which works well (but I hate pumping) and I recently purchased a Platypus Clean Stream to replace the base camp.  The base camp has to darn many problems with filter plugging.  So bottom line for me is Steripen for day use when needed. A base camp filter for evening fill, and that ussually got me through much of the day.  I carry two 1 liter Nalgene's with me during the day.  fyi those weigh 6 lbs full of H2O, including the Nalgene.
SunCatcher

I just picked up a Steripen, however my (Classic) unit came with a screw-on top for a Nalgene bottle.  The screw-on top as a rubberized hole in the middle that the Steripen probe fits into so snugly that you can turn the Nalgene bottle upside down.  This should eliminate "contact" problems for the electrical connectors.  In addition, a screen filter can be screwed into the hole in the Nalgene bottle top, thus providing the means for filtering out some of the particulate matter.

I haven't tried this out in the field yet, but this looks to be a nice improvement for the Steripen option.  (BTW: the new Nalgene bottle top can be left in place on the bottle and the Nalgene cap screwed on the top of that.  And the screen filter can be reversed and inserted in the new top for storage purposes.)

dd

mastertangler wrote on Oct 18^th, 2011 at 4:25pm:

When you submerge the ultraviolet wand on the end of the steripen, it will not activate unless the two electrical contacts at the base of the wand are also submerged.  So, if you don't submerge the wand deep enough or you inadvertently lift it while swirling it around in the water, the unit will not come on (or will turn off).

With the new cap, since you can invert the bottle, there is no way that water will not submerge the two electrical contacts.  But so long as you are careful to keep the wand submerged, any container sufficiently deep to submerge the wand and contacts will work.

dd

BTW:  The directions indicate that you should use either Nimh or Lithium batteries.  My paddling partner has had one of these for a few years and tried it with standard AA's.  It wouldn't come on at all.