A good reason to keep Safari is that once in a blue moon, you might run across a site that doesn't work or doesn't render correctly in FF. It is nice to have at least one other browser installed as a backup/alternative. I regularly use Safari, Firefox and Opera...even IE on my Windows partition, and I like the flexibility.
I don't think Safari is nearly as intertwined into the OS as IE is to Windows, but I would do a lot of research before just deleting it, more than just a casual post on this forum (nice as it is).
I have to agree that if you are hurting for 65MB, you really need to think about jettisoning some of the other dead weight or getting a bigger or external drive.