This is of course assuming the ISP manages their capacity in such a way that latency.etc doesn't go to hell in a hand basket and screw up steaming/voip/gaming.etc
Does the expectation change with regards to where you are pulling the data from? (Given that it's usually easier/cheaper to have more local capacity though IXP's than transit to far flung destinations)
Obviously if you have a slow connection anyway it's easier for the ISP to make that bandwidth available to you, but on faster lines it becomes a lot more difficult to do it whilst providing the service at a price people would actually want to pay.
I have an FTTC connection and generally manage to max it out providing the sending end is capable of sending the data that fast, but equally I have some low end servers supposedly 1Gbit/s ports that often don't get anywhere near that, but given I'm not paying much for that service I don't really expect them to either.