I'd also recommend the sawyer mini. Cheaper, lighter, and I have found it to be more reliable than my previous pump filter, an MSR sweet water. Instead of having to unscrew the entire system to clean, simply backflush with the syringe. 10-20 seconds and you are ready to filter again.

I use mine in a gravity filter setup with an evernew bag as the dirty water bag and a few feet of tubing from mcmaster carr. Depending on what hydration bladder you are using you can hook the filter inline with an adapter, so you don't even have to take the bladder out of your backpack to fill it up. I know camelbak sells an adapter; I assume other companies do as well.

As far as freezing, it's true that it shouldn't be allowed to reach freezing temperatures, but I was under the impression that was no different with the ceramic element filters. Something about water expanding and creating hairline cracks that allow clean and dirty water to mix; maybe that has changed with newer filters.

The only real disadvantage I can think of is that the sawyer mini does not have a carbon filter element, so if you are concerned about any chemicals in your water source, you may want to consider either getting a separate carbon filter cartridge, or going with the katadyn.

As mentioned it can sometimes can be finicky to get water into your dirty water bag depending on the water source, but having something to pour with solves that pretty easily. Could be a ziplock bag or kitchen sink as mentioned. I use the top of a small milk jug cut off. Has a handle and everything.