when to implement VLANs?

There are a few things to look at..
I'd start by looking at the Cisco ports for alignment errors and fcs errors.. that would indocate that there is a duplex mismatch.. If you are using 3Com NICS try setting both to 100 Half.. I've had a hard time getting 3 Com to go to Full Duplex...
There are many other things to look at but I don't have enough information to go on .. like what's your IP scheme.. i.e. do the workstations have to go out over the WAN for DNS / WINS resolution, etc.. if so check the WAN link for adequate bandwidth.. As for the VLANs.. off the cuff, not sure they would help much.. they're most useful for solving problems like workgrouping geographically desparite desktops.. or isolating local traffic,...you may also want tolook at segment traffic with a "sniffer".. see where those delays are comming from....
Hope this helps....

Hi! I don't think VLANs will help you. It is deal when you have huge LAN. Generally switches do all work to send traffic from sender to receiver without affecting each other with only exception for broadcasts. But since you have routers it localize broadcast traffic (until specially configured). So, check routing first. If you use static routing between routers it might become nightmare. With 65 nodes you can use RIP. Then try to analize WAN Links load. You can use MRTG to continuously monitor your links. Link load for more than 80 percent say you have to upgrade link or limit traffic. You should analize traffic pattern between HO and POSs to see which protocols and services create most traffic. For example, you may have documents or application data located in HO, but which can be safely moved to office's servers. So you should analize it carefully.

Good luck.