Updates are always risky. Just read around this forum to see how many users' Jollas have been bricked by OS updates. My old laptop has been bricked by an Ubuntu update at leat twice. Luckily it was relatively easy to unbrick, once I spent a few hours STFWing. I can only assume that something similar would be doable on Windows.

Making an update mandatory and automatic sounds scary but in reality, it changes very little. I would be much more worried if they forced me to use the Metro UI with no recourse to a real desktop.