The main reason for wanting to upgrade is the increased gaming performance 8.1 can deliver. I do not really need it at the moment but I am thinking soon in the future it might be a good idea to have the latest direct-x.
Score another win from a performance perspective. I upgraded to W8 from 7 without changing any Pc hardware and trust me - the under the hood improvements Microsoft touted about are there. On the rare occasion my Pc is powered down fully, it boots up to desktop/tiles within 8 seconds. If it's in sleep state or hybrid hibernate, it's instant on. Everything is far more responsive too, from browsing, music/video and productivity. Gaming is largely the same for the most part though, but it's more stable than 7 if things go wobbly in a game, so I'm happy - coloured tiles and all...
Yeah, I was pleasantly surprised at how much faster and more stable W8 is over W7... you aren't going to notice a lot of in-game performance difference, but it handles crashes and alt-tabbing far better than W7 did. I love being able to alt-tab out of a game, do whatever else I need to do, and then alt-tab back into the game and have it resume play almost instantly. You could do that in previous Windows, but it wasn't anywhere near as smooth in my experience.
For the routine OS stuff, the performance gains are far more obvious. Faster boot times, faster opening and switching of apps, etc.
It's worth the update.