I've switched to XP10 after years of frustration and low framerate on FSX and couldn't be happier. This is really a great simulator, and the best part is that it's getting better and better.
Nowadays I spend 95% of my time flying (at 40-100fps on almost every situation) and 5% downloading (mostly free) add-ons and plugins. Some of them are amazing (CRJ, 777, Simheaven tiles and OSM...).
Back when I was using FSX, it was 75% reading forums to improve my framerate and 25% flying.
You won't regret making the switch, and I'm pretty sure you won't be the last FSXer to do that.