Never seen serps affected by adsense change.
I worked with sites that had adsense with multiple owners and they were changing all the time and have never seen changes in ranking.

It's more likely that you'll see a change in revenues rather then serps.

I switched last year to a corporate account, and my SERPS are all the same or better. No effect from AdSense whatsoever.

Thanks everyone for your answers.

Darkyl, what have you typically seen as far as revenues? I've heard sometimes you see some jumps because your old account might be smartpriced.

Arthur,

based on my experience, I don't think there's a "smartpricing on/off" switch.
All accounts are smartpriced, meaning that CPC is determinated by the account current performance (ctr, conversions, etc) and performance history.
The process requires some time so changes in income for a website may happen if you change the account used for adsense.