Well, let's look at your own list:
- MIDI effects
These aren't new. They've been there forever in the Environment. Logic X has just added pretty UI wrappers around them. That's great - makes them much more usable and accessible. But it's superficial change.
- Flex Pitch
Have you used Melodyne? Any pro user worth their salt already uses Melodyne for time and pitch correction. Flex Pitch is neat and convenient, but it introduces audible artifacts on every source I've tried it on. It's just not very good.
- Track Stacks
This is the worst one: a superficial change that has damaged an important existing feature. The only benefit to Tracks Stacks is it saves you having to manually set up an Aux channel. It has come at the expense of the "Create new track with next MIDI channel" command, which no longer exists.
- Drummer
Gimmicky. It's really just another set of Apple Loops, with little pictures of hipster drummers. There isn't much variability. Imagine how many songs are going to get created with this - all with the exact same drum track.
Also badly damaged is the Environment. They haven't even bothered to update it to the new UI style, which means that existing projects that made heavy use of it now look garbled, and in the worst cases have inaccessible objects off the side of the visible area.
Look - again - I think it's a great piece of software. I'm not griping (or at least not trying to). I'm just trying to point out that there is not much here that's new or innovative, or honestly that useful in the long run. It's fun, but it does it improve your workflow in a professional setting?