The amazing community here were my reason. They essentially passed the proverbial hat and got me bumped up. Mindblowing kindness.
However my reasons for WANTING to upgrade were largely related to MixRecall. I have not had a chance to use it yet (been mostly tracking) but as a novice mix "engineer" the ability to easily compare various efforts to see what I've done right/wrong is a huge bonus. Even for experienced/pro engineers this has to be a massively useful tool. Being able to export any or all of your mixes at once to cart around for testing or showing to clients or whatever is pretty darned awesome.
The Control Bar improvements are freaking amazing and many of those tweaks are things I had been asking for for a VERY long time. It's even better than anything I dreamed up.
As newcomer to MIDI the new PRV was/is looking pretty slick so I was interested in that. Those teeny tiny little blocks were kind of messing me up as well as controllers so it all looked a lot better. I have not tried it out yet but am looking forward to it. The Paint Tool looks cool as well. Kind of want them to create an audio version of it. That would be awesome but perhaps impractical.
More personally I asked some of the folks here to test a very specific bug that had been driving me NUTS in X3 reagarding view jumping when selecting between tracks. It was a MASSIVE slow down for my workflow and was pretty much one of the only things that bothered me in X3. Sure enough it was fixed and I am ever so freaking happy because already it has saved me probably hours of scrolling, double checking to make sure I'm in the right spot and outright temper tantrums (and possibly physical manifestations such as hypertension... seriously it stressed me out that badly).
Everything else is gravy. However the additional AD2 Adpaks allowed me to snag the Fairfax 1 kit which produces a very specific drum sound I have been wanting to duplicate for my own work for a very long time. That of course is the Nirvana Nevermind drum sound. IMO those are probably the best sounding live drums in the past 30 years. Heck... probably ever (but I'm reluctant to leave out Who's Next but they were working with far less back then).
Anyway... great upgrade I think. It is probably more of a cumulative "wow factor" built on more subtle additions and improvements compared to other versions (especially if you are upgrading from X3) but some of these things are very critical improvements for specific users and the on the broader spectrum it's kind of like a slow steady wave of awesomeness washing over us... and we still have 12 months of stuff coming down the pipe.