After years of using Halbert's water filter, brand unknown to me now, I finally broke down and bought my own.  After researching several different brands I settled on the Sweetwater Guardian Microfilter.  Its size was an important factor, as was the ability to add on an iodine cartridge if I wanted one.  But most importantly was the pump built into it.  I found with Hal's the size of the cartridge was almost to large for my hand, and the pump feeds directly into it, a direct up and down motion, making for a tough job when pumping a lot of water.  The Sweetwater's pump handle feeds outward in a lever-action, much like an old fashioned hand pump thus making it much easier.  The cartridge fits easily into my hand and I no longer get that cramp that I did with the older model.
    The intake and output tubes are adequately long enough and the intake tube comes with a float which I found to be most useful.  It keeps the pre filter off the bottom and away from the shoreline.  The tubes fit into holes in the handle, which lays flat against the cartridge when not in use, and you can then wrap them around the whole thing for easy storage.  
    The action of the pump is easy and smooth and it fills a two liter bottle in a short time, perhaps 2 minutes.  Of course it hasn't been clogged yet.  It has an "end-of-use" indicator, and the cartridge boast a 200 gallon capacity.  It also comes with a Pressure Relief System which prevents bacteria from being forced through the system.  It comes with a carry bag, a cleaning brush, and a universal water bottle adaptor, which of course fits none of my bottles, but if I wasn't so cheap I'd buy the ones it did.  I would rate this a 9 on a scale of 10 for ease of use.  My opinion may change after prolonged use, maybe!
    I ordered mine through Campor.  The specs are as follows:
    Weight: 11 oz.
    Flow: 1.25 liters per minute (with new filter)
    Cartridge Life: 200 gals, 7"X2 1/2" (add another 2" for pump attachment)
    $49.95 for pump and one cartridge
    $29.99 for replacement cartridges
    $24.95 for Add-on-Iodine (ViralGuard Filter)