There certainly should be much of an impact in your ranking. However there are a couple things worth considering in this matter:
-Location value: If you are a working on a campaign that is focused on a specific international region then having an IP from that country can be beneficial in the eyes of some search engines in regards to local searches
-Link Value: You'll also want to make sure that you aren't switching to a shared IP which hosts websites that are linking to you already - while in all honesty something that would be extremely rare, if it were the case it would likely lead to the devaluation of those links
-IP History: It's also important to know that you aren't moving to a digital neighborhood that's known in the search engines eyes for housing spam. Think about it like sharing your identity, you wouldn't want someone under your name giving talks about illicit topics. Look up your neighbors with a reverse IP lookup tool such as yougetsignal.com before making the jump.
All in all you likely won't see a big impact from switching your IP address - you just want to do a little due diligence to insure that your new digital home is one that's squeaky clean before moving in!
Cheers,
Adam