It might very briefly decrease your mining hashrate because of the time required to fetch new work from the pool/start working on the new work.  There's nothing you can really do about it though, other than switch to a conventional pool but that might not really make a huge difference in your hashrate so I think you're fine. (it should be noted that p2pool has 10-second blocks so you'll see this message about once every 10 seconds.  That's why you can't use p2pool with devices that take a long time to start new work like BFL singles.)