Thanks for taking the time to comment. I agree that there sure seem to be a fairly high incidence of install problems, so work on improving this would be welcome. I can't comment on why the 3 PC subscription failed you except that you may not have been able to install to the 3rd PC. Support can be great, good, or poor, depending on your problem and I most certainly agree that reaching support, especially as a paid subscriber, needs to be easier.
In your last sentence, removing a PC is indeed easier in 2.0 with the advent of the Multi-PC management feature and the concept of a Circle with a Hub. If you remove a PC via a Hub in OneCare it is removed from your subscription profile on the server and, if it is still installed on that PC, it becomes unsubscribed on that PC.
And, lastly, I agree that being able to cancel should be easier than calling.
-steve