I'm currently getting the following error in my log when trying to start things up for the first time:
connection error to solo (p=0.50): 500 Internal Server Error
You need a line for the "solo" pool in your accounts.conf file, listing your bitcoind username and password (same as in bitcoind.conf, but a second time). You could probably use another pool's login info, as long as you change the "solo" address in pools.conf. The solo pool is used to serve getworks when all other pools are slow/unavailable. These requests are blocking though, so make sure your default pool doesn't go down and has good responsiveness.
If you do decide to remove the solo pool entirely, comment out these lines
...
I did have the solo line in my accounts.conf -- I think that error was a result of my having recently installed bitcoind on this server, and it still needing to catch up on downloading the previous blocks before it would process the requests that Multipool sent its way.
Last night, bitcoind was using 50-75% CPU (and not working with Multipool). This morning, it's almost completely idle (and works consistently with Multipool).
Thanks also for the tips about the possibility of removing the solo pool.