As a long-time holdout, here's my take on 8.1 vs 7.

The only really compelling feature of Windows 8 vs 7 for me is that BitLocker now supports pre-boot authentication with a password, which removed my last obstacle to moving out of TrueCrypt, which I had wanted to do for some time due to it blocking TRIM and VSS on non-system volumes. The TrueCrypt discontinuation notice was the last straw that motivated me to move to Windows 8.1.

I pin a ton of programs to the taskbar in three rows, so the loss of the Start Menu never bothered me as I used it so rarely. (Tip: You can pin Control Panel to the taskbar and pin its applets to its jump menu, so you will no longer miss having Control Panel open as a menu in the Start Menu.) The stupid "Charms" and whatnot can be disabled on the desktop except for dragging the mouse from the bottom right corner; that gesture seems to be written in stone.

I like the Windows 8 desktop UI better, as Aero had become very tired, especially the transparency, which weirdly lives on in 8's taskbar, but I use DisplayFusion to get an opaque taskbar among other things. With Aero gone, I can also now watch WMC video in a window on my desktop without it stuttering, whereas before I'd always have to use my Autohotkey hotkeys to turn Aero off and back on to get clean playback for those times I wanted to browse the web and watch TV.

The Task Manager is finally a worthy day-to-day replacement for Sysinternals Process Explorer.

There's not a whole lot else I find that makes a real difference in Windows 8. It does boot faster, but I don't boot often anyway as I use sleep. If I count the time for my start-up programs to initialize once I get to the desktop, the difference becomes a lot less. And with my SSD, it was about 12 seconds to get to the desktop on Windows 7 anyway, so cutting that in half, if that, doesn't matter much for something I do maybe once a week on average.