I have 50/10 and still have powerboost in the downstream only.
Maybe the reason we still have it is because extreme 105 isn't available in my area. Its just a guess.
I don't like it anyway.
I had some other issues that were resolved by traffic shaping in my router on the upstream side, but later I went ahead and added shaping in my downstream side and it did exactly what I wanted-defeated powerboost. Granted, I don't get the extra "burst", but it sure keeps things consistent:
DiffProbe release. January 2012. Build 1008.
Shaper Detection Module.
Connected to server 188.8.131.52.
Upstream: 10062 Kbps.
Downstream: 112721 Kbps.
The measurement will take upto 2.5 minutes. Please wait.
Checking for traffic shapers:
Upstream: No shaper detected.
Median received rate: 9930 Kbps.
Downstream: No shaper detected.
Median received rate: 49429 Kbps.