a few bad news too
There has been a lot of focus on what Apple fixed with the new release however, they also broke certain things. When you enter fullscreen mode (the new fullscreen mode, your window does not actually stay on the screen that it was. This is very much what iTunes used to do only now every application does it. Essentially you cannot watch a video in QT in fullscreen on one monitor while doing something else on another. Now that is some serious ***** if you ask me.
Also when you have multiple monitors attached, Mission Control does not work as well as you'd expect. You get a separate set of Mission Control(s) for each monitor connected. Yes not really a problem with most MacBooks but most definitely a problem with professional setups.
Launchpad crashes all the time, so lets hope that gets fixed fast. And also the full screen transition animation is too slow. That last one would be a breeze fixing.
Also for some reason back and forward gestures are with 2 rather than 3 fingers now. I get it that maybe it's a bit too many fingers but Apple changed the default from SL and that's just confusing. Good news though, you can change desktop switcher to 4 fingers and then back and forward work with both 2 and 3 fingers. Lets hope that's not a bug
Last but probably not least important, going into full screen mode seems to create a new virtual desktop in some cases. It is a bit confusing because there is no indication of the action and sometimes it is not a very logical one because there are empty desktops
I am sure there are lost of other little annoyances but those are the ones that have gotten on my nerves so far.
My rants aside, application jails is finally here and with Apple's effort and the AppStore, it will make the OS a lot more secure and possibly stable. Unfortunately, the OS is coming out in a month and what we have today is far from being polished. It will take a couple of updates until we get to the usual OS X experience and unfortunately things are just like with previous releases.