Ok... very very nerdy stuff here...
Leopard changes a lot in terms of filesharing:
if you are on a corporate network its kinda broken
if you are a home user, there is some cool stuff under the hood (and tied to .mac)

I'm not even close to anything formal and theres a lot of spelling/gramer errors, but if you are curious (again, not trying to self promot, just needed a centralized place since I'm working with other forums too)
http://tinyurl.com/yuctwy