It's not the money though. If microsoft offered far higher rates for publishers, and far lower rates for advertisers than google does, I'd still be reluctant to use microsoft. The main blocker is that they simply cannot write webapps. The interface for dealing with adcenter is amongst the worst webapps of all time. It's a very very slow painful procedure to get anything done at all. Things you can do in adwords in 5 minutes can take hours in msn adcenter.