Windows 8, incredibly WHOA! That was the VERY first thing when I first installed Windows 8 Developer Preview and it booted into Start, "Whoa!"
Windows Phone 8, it's like Windows Phone 7, but better!
Windows Phone 7, I literally fell in love it. I never actually knew about it until I realized apple won't be doing anything interesting or innovative with the iphone and android to me is just a dog that ate its own poop. I even remember how I discovered it. I was researching info on the latest rumors of the new iphone to see if it would be worthwhile, it wasn't. Feeling exasperated, I was looking at my Windows 7 Desktop with the start menu opened thinking, "I like using Windows, doesn't Microsoft have a smartphone operating system?" They do, and the whole concept of putting PEOPLE, first and at a glace information with Live Tiles just really interested me. Later, I installed the Windows Phone SDK, and the only thing I went through was the All Apps list and the Settings menu, sold I was! Waited out for the best Windows Phone, which was the Nokia Lumia 900 (originally wanted the 800 but that didn't make it to the US) and still love it. I should be getting the 7.8 update soon.
Windows 7, rather pretty. It was like vista, but it worked! My goal at that time was to eradicate every possible instance of vista.
Windows xp, I used it for WAY too long than I wanted to, mostly because I didn't want to buy a new PC to run vista. Did its job pretty well, but holy security updates! I forgot how many there were until I popped it into a VM one day with SP2 preinstalled, and had to install roughly 100+ security updates, just all security updates and probably a dozen performance ones. Then SP3, then MORE security updates!
Windows vista, I skipped it as it was just a constipated dog that ate its own vomit. It was SUCH a pain to maintenance and troubleshoot some of the PCs that ran it at first launch, and even after SP2.
Windows 95, my first and earliest Windows version I ever used. The '90s were such awesome times! At the time, 95 was like the Windows 8 of UIs and PC technology. It changed the GUI for the overwhelmingly better and made computing what it is today. It had its issues, but that's what happens when old code from DOS is used to run an advanced GUI. I recently watched this cheesy video that was a video guide to Microsoft Windows 95 (remember when people just to call things that, Microsoft Office, Microsoft Windows Internet Explorer?) It was weird to look back on how plug and play operating of devices meant having to exit Windows, manually turn off the PC with a kill switch usually in the back, plug in the device (giant ports galore), boot up the PC, pop in the driver CD after Windows recognized the new device, install the drivers so Windows knows what to do with it and what it is, and if it was a printer you had to go through a wizard to finish it off. Holy steps! Now, with Windows 8, you literally can just take a device and plug it in and seriously most of the times have that device, from a wireless adapter to printer, be working and functional in a few seconds. Plug and play!