Although there's nothing like the feeling of crumblin herb with your fingers, grinders can be pretty neat to have. My vote goes to Sharpstone, I have the 4-piece "clear top", it was about $20 on eBay. Great deal compared to the traditional Spacecase. Construction seems very solid, the glass in the top doesn't seems fragile at all and I love being able to tell when to stop grinding. The pollen catcher seems to be doing a pretty respectable job, the screen isn't too fine but personally I'd rather have a greener kif and have more of it than have pure white but taking forever to accumulate.
To help accelerate kif collection in my experience putting the coin or what have you in the herb collection chamber and shaking as well as keeping your stash and grinder in the fridge both work great. Never had issues with humidity or anything, in fact, I would even suggest it (I use Ball jars, pretty much identical to mason). Outside of the fridge I
have had issues, never mold (which is def. possible) but sometimes just getting very dry. If you store in jar, you can always put in a few slips of paper to absorb moisture if you notice condensation, or citrus peels/celery if you believe its drying out. Frozen, herb will keep for at most 2 years, otherwise, you should enjoy it 4-8 months after harvest.
Don't forget to knock it all down when you are done grinding. In fact, the sound of a metal grinder being banged against floor is like the signal in my house that a session is about to begin. Make the knocking sound on the floor and suddenly there's knocking on the door until the room is decided to be at capacity.
I can post pics of my grinder as soon as the semester starts again, but why bother when you can find it on eBay:
http://cgi.ebay.com/SHARPSTONE-2-5-...21969885QQcmdZViewItemQQptZLH_DefaultDomain_0
FWIW This isn't the seller I got mine from but I've never had problems on eBay anyway. Be sure to shop around to make sure that someone else reputable doesn't have the same item at a lesser price, or with lesser shipping.