I have a Verizon FIOS connection at home (fiber optic to the home, 15 Mbps down / 3Mbps up), and since Apple's description of the Broadband Tuner app specifically mentions FIOS connections, I thought I'd try it. However, FIOS is not a high latency connection -- ping times on FIOS are under 10Ms to on-net servers and no more than 40ms to any good server on a tier-1 connection.
Tested with Verizon's on-net speed test server:
http://infospeed.verizon.net/fttp
Safari 2.0.2 / Empty cache before each run (speeds in kbps)
BEFORE Installing BB Tuner
Three runs: 147843 / 156862 / 155172
AFTER Installing BB Tuner
Three runs: 156862 / 156182 / 155171
So, no difference. I'm un-installing. If BB Tuner does what it says, it is NOT for FIOS connections, since they have a very LOW latency (which is what you'd expect from an all-optical PON).
Later,
Mike