In fairness to VM their network is oversubscribed in my area and has been for over six months. Someone has probably worked out it is more profitable to raise prices and accept a small reduction in subscriber base than segmenting the network sufficiently to make the speeds they are selling a reality.
For reference, my 350/35 service is perfectly good between 2am and 2pm, correct signal levels, no errors - but the low point is around 8-9pm when I see download speed as low as 37Mbit, with a median around 120Mbit.
One of these days I need to take a typical daily domestic usage curve and extrapolate how much demand is on their network in my area given the shared bandwidth of 32 DOCSIS frequencies at 40? Mbit each. What I haven't been able to find are statistics showing a typical domestic Internet demand distribution - i.e. of 1000 subscribers having access to a 100Mbit connection, how many are effectively idle at peak time, how many are just consuming 10Mbit or so for streaming TV, and how many are saturating the link.