So far so good. It took some work to get the channels set up that I wanted, but now that it's up and running it has been trouble-free (about five months now).
I read a few complaints about ads loading slowly, so I put the OpenX code snippets into sized divs on the theory that the browser could load the rest of the page around it if ads were slow to come in.
One of the biggest things I like about it is the geotargeting. I can run my own banners targeted to certain countries, and AdSense everywhere else. In effect, AdSense is my universal default, then I can add advertiser or affiliate banners where suitable.
Another thing I like is that the OpenX code conceals AdSense IDs and affiliate codes.