Thanks again guys for the help. "usuexit" is now online, and should be functioning properly, but there seem to be a few mystifying issues:
1) TorStatus marks it as "hibernating" which it clearly isn't; it's online and accepting connections. I'm not sure what made TorStatus think it was offline.
2) For the first nine hours it has moved about 12 MB of data. I would think it would be more than that, especially for an exit. There's a blog post outlining the growth rate for guards, but how about for exits?
3) There are mysterious warnings in the log:

Jan 30 21:57:36.000 [notice] Circuit handshake stats since last time: 0/0 TAP, 50/50 NTor.
Jan 30 22:57:36.000 [notice] Circuit handshake stats since last time: 0/0 TAP, 31/31 NTor.
Jan 30 23:07:29.000 [warn] EXTEND cell received, but not via RELAY_EARLY. Dropping. [4 similar message(s) suppressed in last 3600 seconds]
Jan 30 23:07:29.000 [warn]   (We have dropped 95.24% of all EXTEND cells for this reason)
Jan 30 23:57:36.000 [notice] Circuit handshake stats since last time: 0/0 TAP, 39/39 NTor.
Jan 31 00:01:41.000 [warn] Got headers "HEAD / HTTP/1.0\r\n\r\n" with unknown command. Closing.
Jan 31 00:57:36.000 [notice] Circuit handshake stats since last time: 2/2 TAP, 41/41 NTor.
Jan 31 01:04:46.000 [warn] EXTEND cell received, but not via RELAY_EARLY. Dropping.
Jan 31 01:04:46.000 [warn]   (We have dropped 95.45% of all EXTEND cells for this reason)

I'm familiar with the meaning of the "EXTEND" cell, but I'm not sure what RELAY_EARLY is, nor do I know what this warning means. If the relay has an exit policy, why are circuits being extended beyond it? Hidden services, maybe? Basically the log has more warnings in it than it should (at least based on my experience with regular relays) and I'm not sure why. I tried restarting Tor, but the warnings still appeared. Any ideas on what I can do about them, if anything?

Thanks,
Jesse