For myself, I have the Telo behind my router and QOS on Telo set to zero.
I have no issue. My up and down speeds are what I expect from my ISP. I get 6.5 down and 1.5 up which is what I pay for.
YMMV, and I may be an exception. But it does stand to reason there may be a small degradation of those speeds with a call in progress.
IMHO and it is only my experience, but I think most of the gripes are pickin fly sh*t out of pepper.
Fire at will (but please don't shoot me)
P.S. I just wonder if anyone here who has switched from Vonage or any other VOIP, would care to post some stats.
Curious minds want to know.