Ok, what it means is:
If you buy their internet performance package at say 6 mps. That means you should get files transferring at 6 megabytes per second. That means if you download a 6 megabyte picture, it will complete in 1 second. Or so they tell you. What they've all been doing is if (I guess through software monitoring) they notice you downloading a picture or video or movie or playing an online game, where you have a lot of data going up and down, they will throttle it or slow it down.
For eg: since I've been with bell, and download torrents, I have rarely been able to get about 20 kbps. That's .02 mps or less than 10% of the speed they are charging for. I also noticed when I played battlefield bad company online, I was always 2 seconds behind everyone else. That is because Bell (and others) are throttling the speed in which data gets to and from my computer. Even though we are paying for a high speed connection....
This is one of the things that made me finally realize that our elected officials really aren't out to look out for us, the citizens. Bell et al have been doing it for years, and the CRTC did squat about it.
How long do you think Bell et al would be able to get away with it if they were applying the same logic to telephone service? For example: if Bell et al "decided" to limit your calls to 2 minutes or less? Or if your call went over 2 minutes, they'd cause so much static on the line that you couldn't hear what the other person was saying?
Another example: You buy a new mustang GT500. It is rated at 460 hp. So you like to accelerate quickly onto the highway using 460 hp to get up to highway speeds fast. Ford installs a monitoring device on the mustang that sends them a signal whenever you press down hard on the gas peddle. When they notice you doing this they retard the timing so you don't get 460 hp, you only get 200 hp and the mustang slows down to Kia speed.