I have been in the computer field for a few years. It is how I have made my living. My dislike of Microsoft comes from these experiences.
1. Apparent lack of quality. I pride myself on my work ethics. I do my best to fix a problem properly, not just put a band-aid on it. In my experience when clients brought a computer for me to repair, I knew it was just a matter of time before the Microsoft OS based computers came back again, for another computer. People with MACs, Linux based PCs, and looking back, Amigas, and so forth, had stable systems, meaning they did 'break down' BSOD or the equivalent, nearly as often. I hated working on someone's Microsoft based PC knowing when I returned it to them, that I would be seeing them again in another six months or so.
2. Bloat. In the late 80s, I was using a fully multi-tasking OS, on a high resolution, high colour, monitor, with a full GUI interface, being able to format a floppy, while rendering a 3D image, all doable without a harddrive. A single floppy drive and I could do all that on my Amiga. Microsoft did not offer most of features found in the Amiga OS, until Windows XP. Windows 2000 did offer a number of them. There are still at least one nice feature of the Amiga OS, that is not yet duplicated by Microsoft. Even now with all the abilities, Windows XP needs 128MB of RAM and a GB of hard drive space just to turn on. My old Amiga worked very nicely with only 512KB of RAM, and a single 880KB floppy. At 1/256th the RAM and less than 1/1024th the storage capacity, that old computer matched capabilities with a current low end XP. (Unfortunately, Commodore's inability to market successfully brought the company down.) Currently I use linux, a fully 64bit OS with almost if not all of my software built for 64bit processing. All my linux software takes up much less hard drive space, and seems to use less RAM than the equivalent MS products would.
3. I could go on about the system security, liking the underdog, and so forth, but I will leave it at that for now.