Anyone used the katadyn carbon cartridge?

I've never used it, but it looks like it would work pretty well. It's not a filter, but uses activated carbon to remove some tastes, and it looks like you can attach it inline with a hydration pack. The other nice thing about it is that you can replace the carbon afterwards without buying a whole new cartridge, which seems a lot more reasonable to me. I have read that with other filters (katadyn hiker, msr miniworks), the activated carbon stops being effective much earlier than the filter element itself, so you are stuck either using activated carbon that stopped removing chemicals long ago, or are forced to buy a new filter cartridge.