I just upgraded my work MacBook to Leopard and are handling the few settings needed to get it to work swell in the windows network in my office. For me, I had bookmarks for the two shared servers that I need access to, and those were still available to me. But, many have had problems mounting Windows servers on Leopard, when it worked for them in 10.4. I think macwindows.com is a great site for such issues, and they have a Special Report on Mac OS X Leopard Cross-Platform Issues summarizing the various solutions that have (and have not) worked for folks.
Now, I'm still working on getting the printers to work. It added the LaserJet easy enough, but when the printer receives the item to print, I'm getting a blinky orange light and that's all. *shrug*