I was interested in checking it out, but WinXP is not supported.
This tool, like xperf, takes advantage of new metering features introduced with Vista. So it's a no go for XP. Under Vista and Win7, the information that can be logged now is really detailed, but analyzing it is a chore and sometimes you just flat cannot find the name of the offending DPC.
LatencyMon, could be very handy if it saves having to pick through the xperf report. It would be especially useful if it can resolve the "unknown" drivers. These are the ones that drive Win7 users nuts.
For XP, you can use the older kernrate utility. You don't have as much data to work with, but it will usually guide you to the culprit when you're diagnosing DPC latency under XP, especially if it's one of the usual suspects, e.g. a network driver.
There is also a companion tool called krview, which formats the kernrate output and supposedly makes it easier to comprehend, but I have no personal experience with it. Maybe I'm a masochist, but if there's a long way to do something, that will usually be my method of operation. :)