I'm convinced it's near impossible. I've had a CTR of ~ 15% on a few keywords and it reduced my bid by a whopping 8 cents. It seems they've based their minimum bids on historical bid data. Basically, if they've been getting $1.25+ consistently for months, they won't accept anything less than $1.00. They are under the impression that this is the answer to their financial woes. I'm convinced they're losing advertisers to Adwords though. Why pay Adwords prices and get Yahoo volume?
I will say one thing, Yahoo's traffic is always good for promoting to less-technically savvy crowd.
They promised sub-10 cent bids and have done nothing but increase. I say we boycott!! Easier said than done if you're profiting with the traffic still though.