I just bought a nice grinder after using a two piece wood Greenleaf grinder for years. It worked great, but would get bound up as the kief would stick to everything inside and would need to be cleaned about every 1/4 oz or so. I figured instead of going through all that I could collect a nice treat in the process.
I bought a cheap grinder from Gotvape .com, which was a knock off of a Space case for about $40, which they fucked up and sent me a grinder that was 4" , I could grind a 1/4 in that bitch, I sent it back , too big and cheesy as hell.
I did grab a Sharpstone off ebay for $35 with a pollen press, definitely a great buy and good quality. I gave that one to my brother, he is very happy with it.
I decided I wanted to buy the best for myself since I will never need to buy another and in my 20 years of smoking I have never had one, figure I am worth the $74 I spent on the med Space case. This thing is great, not sure why I did not get one of these years ago. It is a very small investment, and I really like the texture of the grind, as well as the quality of the kief, some of the cheap knock offs will add aluminum shavings for you as well. Also the kief screen on the better grinders is much finer than some of the knock offs which will give you a green half kief half bud mix.
These are four piece grinders tho. I read everything I could find on this and five other ganja boards and the two best were the Space case and the Mendo mulcher, that being said if $ is a concern that Sharpstone with the pollen press on Ebay is an excellent deal and a really good quality grinder for a great price.
They are spendy for something that just grinds bud, but I think it adds to the overall quality of the smoke with a perfect uniform grind every time, with a nice treat at the end of the bag.
Here is the best value deal I found
http://cgi.ebay.com/NEW-2-2-SHARPSTONE-Herb-Tobacco-Pollen-GRINDER-Press_W0QQitemZ370107248985QQcmdZViewItemQQptZCollectibles_Tobacciana?hash=item370107248985&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318