List navigation and search engine optimization

Folks,
My understanding is that websites utilizing proper CSS list-based navigation are real search engine magnets. (Sorry, Flash).
Suppose the menu buttons using actual text for captions are substituted with images for the sake of increased control over the appearance because you’d want:
[LIST]
[]Buttons to be icons with symbols, not text
[
]Fancy non-standard caption fonts either to allow stylization going beyond what CSS formatting has to offer, or avoid dealing with embedding and cross-browser compatibility issues
[]Anti-aliasing not to depend on the end machine’s display settings
[
]Custom GIF-animated roll-over effects and such
[/LIST]
Doing this would obviously hurt the visibility of the site to Google and the like.
The question is whether the use of image alt tags would restore the site’s “spiderability” or not.
Thanks