For 07 GOOGLE will allow you to have competing ads for adsense.
Since its inception, google has forbidden adsense publishers from having additional ads from competeing networks on thier pages.
Its all different now..whereas you used to NOT be able to have other ads along with adsense on a site, now you can have any other ads, you just need to change the color or take other methods to make sure they are not confused with Google ads.
See Google TOS or check out this link https://www.google.com/adsense/support/bin/answer.py?answer=32849