We had Virgin on cable for many years, we started off at 1MB and every so often they upped the rate. Once we’d got to 10MB, everytime they did it I rang up and dropped down to a cheaper rate.
Eventually the cheapest rate was at 20MB. Worked fine even with Xbox Live, and a couple of PC’s surfing plus Sky On Demand downloading.
We moved house and the maximum line speed we can now get is about 3.5MB (rural).
While the On Demand programmes take longer to download, usually 15 mins before you can start watching them; everything works just as well as when we had 20MB.
FWIW – my first modem ran at 2400bps 🙂