Vagueness is gone. I run my '11 road glide ultra often at 100 mph-plus when I'm in the middle of nowhere, which I often am.
It tracks solid, and true.
Even at top speed (110-115ish) it's steady. The chassis could handle much more motor.
Now, at harder corning at higher speeds (80-85) my bike will start to give a litttle gentle weave on bumps. Nothing frightening, just a hand on my shoulder saying "son, that's enough".
For example, a few months ago I went both ways on I-80 east of salt lake city...sort of a high speed set of turns going up (or down) the mountain. Traffic was moving out both times, and I was in the fast lane, but at 85 mph I wasn't wanting to go any faster down the mountain.