I also posted this in the Ontario Highways thread, but looks like it may be more appropriate here:
I wondered what locals thought of this when I drove through there last month. I was surprised to see the limit was only 100 along the entire length of 401. Having foreign plates, I tried to stay under the radar by setting cruise at 110, and had to stay out of everyone's way because I was getting passed by everyone, except some trucks which likely are governed to do the limit. I can see how this can cause some problems.
Here in the US speed limits are typically 65 or 70 mph between cities, and go up to 75 or 80 mph out west. I've also driven in the UK and Ireland which has speed limits of 70mph and 120kph on their motorways respectively. I've found that where the speed limits are higher, you tend to see less variance in the speed of traffic. You're always going to have a few menaces weaving through traffic at 150kph, but the majority of the traffic stays in a narrower speed range and results in smoother, safer flowing traffic.