Google Adwords is in the process of introducing a new bidding option. The bidding option will be called "Preferred Cost Bidding" and will act in pretty much the same way that "Position Preference" does except with bids.
Basically, instead of setting only a final "Maximum" bid you can set a "Preferred" bid and let Google auto-optimize for you. The system will try various positions and try to deliver an average CPC (or CPM) as your preferred bid. Both of these bid options (Max & Preferred Bids) should help SEM managers to fine-tune their accounts even more.
Google is releasing this feature under the "Edit Campaign Settings" page over the next few days.
Cheers!
Sasha