User Review: MSR MiniWorks EX
Price Paid: $89
Overall, this is an excellent product. When used properly, it will do a great job of providing potable water (where viruses are not a large concern).
I've had mine for over four years now. I take it on about 10 backpacking trips each year ranging from 2-10 nights with no failures yet. I also take it with me on longer day hikes and mountain biking rides where I do not want to carry too much water due to the weight.
While the pump filters might require more effort than some of the gravity based filters, it does allow you to draw water from much shallower sources of water (and the occasional puddle) than a bag will do. The ability to screw it directly to a Nalgene bottle or an MSR hydration bag is also pretty convenient. Attaching directly to the bottle or bag lets you use both hands on the pump without worrying about your water container falling over and spilling in the process. If you do not have a Nalgene bottle or MSR bag, you can also put the exit tube in any other container that will hold water.
I've read where several users have expressed frustration at the pump being hard to pump or the filter needing to be cleaning frequently. This is caused by siphoning water that has a lot of particulate in it. Naturally, the more particle to be filtered, the more resistance the filter will have.
I avoid this problem buy putting a bandana or other small cloth over the intake "spring". This serves to prefilter the larger particles before they get to the ceramic filter. If less gunk makes it to the filter to begin with, less gunk will need to be handled by the filter. Users should be careful in choosing their water beforehand. Still green or brackish water is much more likely to have viruses and other contaminants than clearer fast moving water.
One note of caution. If you choose to use this during sub-freezing temperatures, you'll want to try to keep the filter warm. Sleep with it in your bag or carry it deep in your pack. If not, the filter will freeze and be rendered useless until it properly thaws. You'll also want to make sure the inner chamber is dry to prevent freezing as well. Freezing and thawing can crack the ceramic filter.
All in all, this is an excellent product. I'd give it 5 stars were it not for two shortcomings. Weighing in at a pound, it is not the lightest most compact solution, and its ineffectiveness against viruses.