Its a good question, that I will try to find the answer for. The problem isn’t only limited to network printing, it also involves slower access to network shares, programs running slower when checking documents on network shares etc.
The solution to the slow network printing is however quite simple. I would love to know how he came up with it, but in any case – Pavel posted this solution in microsoft.public.windowsxp.print_fax some time ago:
I had the same problem and have found some workaround for limited number of network printers. At command prompt type NET USE LPT2 \\computername\printername password , and the port lpt2 will be assigned to the network printer. After that port assignment in the Printer Properties has to be also changed, or, if the Properites are too slow, the old printer deleted and the new one with LPT2 added. LPT3 (or maybe another port name) can be used for other printers.
After this assignment, I can access to the printer list and printer properties as fast as before SP2. However, this is not perfect solution and I hope that some patch from MS will appear.
PS: I have found that just adding the local ports with the comands
NET USE lpt[number] \\networkshare\printer
is enough, at least for the networked Epson laser printers I am using. No need to change the setup after adding the local ports.