Hah, I just got my first fixed gear set up this week. It's been a learning curve for me as well. I keep forgetting it's fixed and get bucked a bit by the pedals when I try to coast. I'm really surprised by how tall gearing a lot of you guys push. I've got 39/16 and it seems perfect; If I went to a 44 or 46 chainring I'm pretty sure my knees would be super sore.

edit: Also, I have a 1/8" chain and cog, but 3/32" chainring like one of the posters above. Could this be causing a slight chain buzzing sound I'm hearing? It's only occasional, and when I hear it, it is still a bit more quiet than my geared bikes.