I've been using my phone to tether since last September and it's generally fine. Those that complain about latency issues with a sub 100 latency are talking rubbish. I'm no worse on 80ms with 3G than I was with 20ms broadband, it's subjective and down to each person and their reactions.
Haven't found bandwidth issues with any game yet ranging from FPS, RTS and MMORPGs...
You stated that people complaining about 100msec latency vs 20msec are talking rubbish and then admitted that it's subjective. Some (myself included) would notice the difference in an FPS game or the like.
The issue more with 3G is that sometimes you'll get far over 100msec latency.
Those that complain about latency issues with a sub 100 latency are talking rubbish