Microsoft has been pissing off their customers in a fun product called Vista. Using your tanker analogy, Microsoft has a huge gaping hole on the side of the ship. Its not going to stop them, it will slow them over time but its them bleeding customers.
People are starting to look for alternatives. I couldn't believe it when I saw 2 friends of mine, who have next to no technical knowledge purchased a laptop and installed Ubuntu on it. I almost fell out of my chair when I saw it.
There are also lots of people switching to Mac or wanting to switch to Mac. Lets face it, Apple is more expensive because they don't have a low end machine. They don't want to fork out the money right now, so they are just waiting. Will they switch ? No idea, but the ones who have made the switch haven't been happier. Hell, I am one of them.
There are alternatives and many people are eye balling them. If Microsoft drops the ball on Windows 7, that hole in the side of the tanker is only going to get bigger. Don't get me wrong, I totally agree that it would take a major event for that hole to sink the ship.