I open Windows Explorer and enter an IP for a computer on my home network (\192.168.1.101). It takes 30 seconds or more to present a list of the shared folders. Once they appear, navigating through folders and opening files is fast.
Suspecting that the remote computer was being automatically indexed or something, I went into Tools->Folder Options->View and unchecked "Automatically search for network folders and printers," but that made no difference.
All computers involved are running Windows XP.