Hey Zachary!
It's a good idea to use pure css menus when the design and functionality are the same as using a menu with javascript AND the actual menu items are in a clean
html list (not delivered through the JS). But keep in mind that cross-browser functionality can be an issue with pure css menus. Internet Explorer is a real problem in this regard.
As for SEO, I doubt inline javascript that adds functionality to a clean html list will make search engines burp. We used to worry a lot about that like 5 years ago because JS used to cause slow load times, but nowadays the Internet is a lot faster, servers are faster, caching is better, etc... All the same, it's good coding practice to remove inline JS from HTML.
If you want something fast and cross-browser supported look for jquery menus. There are free samples all over the place and they are brilliantly fast and you can list your menu items in a plain html list (the important thing).
Happy coding... - P