* The use some kind of swarming protocol, kind of like bittorrent, to distribute updates. This means that they use your bandwidth to deliver their updates to other users. What makes it worse, the people who cares the most about updates are organizations, and they will block that function, so they will not take their part of the load.
* If you run an earlier Windows, it downloads the Windows 10 update to your hard disk, just in case you'd want to install it. This uses a lot of disk space and bandwidth. I suspect the real reason is to provide more sources for the swarming protocol, as a described above.
* They have a feature which allows them to stop certain programs from running if they don't like them, and even remove them. Cloaked under the disguise as anti-piracy, it is bound to harm legitimate use as well (such as using a cracked version of a game to make it work because they've effed up so the originals no longer work). Also, it would be trivial for them to say "We don't like LibreOffice and OpenOffice, they compete with MS Office. Let's block them.".
* They seem to have removed the option of "Don't install updates", only providing "Download and install" and "Download and install later". This is a huge risk, as it allows them to, at will, replace just about Everything in the operating system or on your disk.
* It has tools to redirect "unsuitable" internet sites to other sites. It would, for example, be perfectly possible to use this to block, say, Wikileaks, and redirect to, say, NSA.
