Yes! We recommend that any site serious about their rankings spend the money (it's only a few extra bucks a month) to be on a dedicated IP.
It’s important for a few reasons. First, we’re pretty sure it plays at least a small part in the search engine’s algorithms. The engines will use reverse lookup to determine what kind of IP you’re on. If you think they don’t care, consider this: It’s been said that about 3 percent of all Web sites have dedicated IPs, with the other 97 percent resting on shared IPs. Research was then conducted analyzing the top 50 results for certain queries in the various search engines. The research found that 90 percent of the top-50 results were using dedicated IP numbers.
One of the reasons using a dedicated IP can have a positive influence on rankings is because the engines take into consideration how fast your site loads in comparison to other sites. If you’re sharing your IP with 500 other Web sites, the server, like all good customer services departments, will deliver the files in the order they received them. If there are 10 people ahead of your visitors in line, they’re going to have to wait, resulting in a slower page load times and frustrated users.
Sharing an IP address also doesn’t allow you to control who your neighbors are. If you’re sitting on the same IP as a gambling site, a porn ring, a Viagra dealer, and a priest, and one of those addresses gets banned by the search engines, you’re banned too. Search engine’s don’t just ban domains, they ban whole IP ranges.