I tried to sync a local directory on my WinXP computer with a remote directory on a SMB share (powered by Samba).
There were many files in my local directory (3300 files using more or less 300Mo).
After some time, when a certain amount of files have been transfered (between 1000 and 1500), the sync process becomes very slow : less than 10 files a minute.
Together with the impossibility to pause the sync process, it becomes prohibitive.
Eventually, I took off some files and I restarted. To transfer 2000 files it took more than 7 hours !