They work well, they are just on the heavy side. I've used the MSR Sweetwater Purifier, and I've also used the Katadyn micro filter. I've also used the MSR Hyperlight
My favorite was the MSR sweet water purifier. You could practically filter mud, and it came out tasting fine and looking clear. I'm not a fan of the other 2 purifiers i listed, the katadyn doesn't filter as well, and broke on me, while using it in the boundary waters...So i boiled all my water. The hyper light, basically uses paper filters, that seem to clog quite often, while easy to use, it can also be a pain. The problem is, the sweet water is very heavy, and is also slow to pump.
For Philmont, You would be fine using polar pure, or aquaria to whole time. You may also look at using a steripen. I recently used one for a month on the AT, and liked the simplicity quite a bit.
One thing to keep in mind, is that if you use a pump, you will need more then one pump for the group. because, otherwise, water stops will take forever. If you use aquamira , you just put some drops in everyones bottles and then you are on your way.