The discussion could use a little more information, like are these short phrases that aren't doing as well or are they longtail phrases?
Are these ecommerce BUY related phrases, ecommerce REVIEW related phrases or are they non-commercial?
What does your title and meta description look like? How well optimized are they? My ideal (and kind of funny actually), I style my title and meta descriptions just like an AdWords ad. That's done not to blend in but to enhance the CTR performance.
I agree with the OP that an ad that goes north has the opportunity to bring in a high percentage of CTR. But to answer the OP's question, I don't think the first place position is worthless.
I find it frustrating to see non-relevant ecommerce ads jumping to the north position, too. Fortunately, those positions aren't permanent, they usually drop off.