Right, the only metric I want to see is the roundtrip latency between when I submit my order to when I get my execution report. I just aggregate the timestamps in my FIX logs and usually quote the min, median, max when trying to compare exchanges.

Every exchange we negotiate with quotes us their ping-test results. I always have to remind them that there's a lot more to getting an order into the book (especially via FIX) than just TCP.