I don't use them, not even with my Vauen. I hate a hard draw, and I really don't care for charcoal filters. The balsa filters draw better, but I don't see the need.
Yes, they have a strong smell of ammonia and the paper turns brown, and maybe moist depending on the level of moisture in the tobacco. IN meer pipes, since they absorb a lot of the moisture, the filter is less likely to go wet, but I recommend changing the filter every two smokes any way. On larger bowls I may change it after each smoke.Do the meerschaum filters really remove " toxins and nicotine" meaning do they color brown and smelly
as much as the charcoal filters, assuming that you have tried both?
I like to think about them as mini reverse calabash pipes, since there is a small chamber for the expansion of the smoke.