Just polling here out of curiosity, and, I guess, sort-of as a bit of market research to see if it'd be worth my while to type up an epic guide to improving latency.
Go to
DPC Latency Checker , download it, and tell me what the results are. List your OS, CPU, chipset, and anything else you care to list too so we can see if there are patterns.
Mine, to get things rolling, goes like this -
OS: WinXP SP3 (general purpose install)
Form: Laptop (Dell Vostro 1710)
CPU: Core2Duo 1.8GHz
Motherboard: PM965
Typical latency: 230us
Peaks: ~3000, every four or so seconds