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I use samba shares on linux, HPUX, AIX and Solaris on a regular basis. Never had problems. I use Fedora 7 as one desktop, no problems.
Samba is developed on a build farm. There are a number of different flavors of *nix that run automatic builds of the Samba tree. The contributing developers use whatever platform they happen to be comfortable with to write code.
To answer the underlying question, Linux is the kernel. Samba is tightly integrated with the kernel, so to seek out the distribution on which Samba “works best” is probably a waste of effort and time. Support, however, is another matter. One of the commercial Linux distributions (Red Hat, Suse, Mandriva, etc.) is probably going to have the best support structure for Samba (i.e. nifty GUI configuration tools, telephone help, and so on).
I have used Samba on every flavor of Unix but AIX and probably a dozen Linux distributions. I have yet to notice any substantial difference in the way it works.