I am in the process of testing out hosts for my domain to see which host can, within my budget, handle the load my site will be putting on their servers and this will require me to update my nameservers about 3 or 4 times--but I thought I remembered reading somewhere that frequent changes to your site nameservers may have a negative effect on your overall SEO/SERP?
It would only effect it if you have downtime during the propagation of the name servers, make sure to not have any downtime on your site. You can do this by leaving both servers or accounts active for atleast 72 hours before removing the web page files from the old server.