We do very little wave soldering, maybe once a week. We have been running a Novastar Spartan 8S for years with very good results. I do wish we had the wider 12S for the wider boards, but it has only come up once in 7 years.
I think there is a lot to be said for running a small wave solder machine like this. With less flux and solder you can keep the machine very clean with fresh flux and solder, much easier than a large machine. Heat up time is minimal and with little pot contamination due to the small pot and fresh solder, the solder joints are great.
But to your point on complex boards, we really have not run anything too complex.
These machines are around on the used market as well, often with very little use.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=52218)