My sram chains get about 3k miles, which I guess is ok. I have heard people complain about shimano chains wearing quickly. Those who keep their chain the longest seem to be running campy.

KMC has the most mixed reviews I've ever heard. Some people swear by them, and I know a mechanic who swears KMC stands for Kant Make Chains.

of course, chain wear has so much to do with how you ride, how you maintain, and what you ride in that any useful comparison of chain life needs a lot more than brand attached to it.