I have been using OS X Mountain Lion Preview 4 for a while now, actually just upgraded to the GM build. Figured I should finally publish this post. The install was flawless much like installing Lion was directly from the App store.
Once installed it seemed to be a bit more snappy than Lion was, which is nice seeing that I personally feel on my Macbook Pro that Lion was a step up in speed from the previous OS as well.
A few things I noticed is that X11 is no longer included with this build, instead you have to use XQuartz which is no biggie. Info on this can be found at their wiki and the newest XQuartz that was available when I did the install was X112.7.2 – XQuartz 2.7.2.
One thing that was not really clear during the install was getting my Twitter account setup within Mountain Lion. I found the following information on how to set up my Twitter account within Mountain Lion here.
Once you have installed Mountain Lion you might notice installing 3rd party programs that were downloaded outside of the App store wont install. Its a little annoying but it does help with the security of the operating system, especially for new users. On the other hand for power users and others that need applications found outside of the apps store you need to disable Gatekeeper. I came across the following article that detailed out the steps of doing so, its actually quite painless.
My only gripe so far with Mountain Lion is the notification center, while I love the idea of it I hate that its not very configurable. I love Growl and have it themed just to my liking etc, you just dont have that ability with the Notification center. The Notification centeris either just on or off, I hope that some tweaks come out to adjust the overall look of the popups or that Apple comes out with a Growl type preferences pane for the notification center.