Pros Messages, if you really need it i guess
Cons -Safari 6 seems to have trouble with some sites (not adobe flash)
-Notification center is mostly unnecessary
-Facebook integration is NOT supported at launch day
-Parallels 6 is not supported or compatible
-NO AIRPLAY MIRRORING FOR 2010 MODELS
Summary I am so very tired of Apple releasing products that are not completely ready (i am referring to FB integration that was shown in the videos on launch day). I am also so very irritated with Apple for showing off features and then not making it clear that older models are not supported (airplay mirroring) This was the biggest reason i purchased the stupid upgrade and i cant even use it!
Parallels 6, as i mentioned no longer worked once i upgraded forcing me to purchase Parallels 7 (more of the parallels company's fault, but still annoying).
My battery seems to heat up faster than with Lion, not sure why this is but i will be monitoring it closely to make sure there are no problems.
There was absolutely NO reason for me to upgrade from Lion to ML, honestly i don't even need Messages nor can i use Airplay mirroring and i could not care less about the notification center. I don't really care what anyone says, 20 dollars is 20 dollars and if i had known better i would not have spent the money. Do your research before upgrading!
Pros Overall, I like Mountain Lion.
Cons I cannot run Adobe Bridge CS5 without it crashing every time I start to look at thumbnail images. I have tried work arounds, but no luck find one that works consistently yet.
Summary I would not have installed Mountain Lion over Lion had I known I was going to end upnot being able to use Adobe Bridge.
Pros Twitter integration, Airplay, iMessage, Notes, etc.
Cons A little lag when using airplay.
Summary Mountain Lion is a great operating system, but with every major update, it still has a few tiny bugs. Apple has been doing a good job of bringing iOS features to OSX. One feature I found (that may or may not be new) let's you schedule when you want your mac to turn on and off. I quite like this update.
Cons Nothing Yet
Summary This is a solid upgrade from Lion. It seems like a more polished version of Lion. The ICloud integration with Reminders, Notes, Mail, and everything else is very helpful. One of the cool things that i noticed is the new dock, it is a different color, and also the light below the app that shows which apps are open is now a bar at the bottom of the dock instead of a round circle. In Launchpad it is great to be able to search for my apps, since i have lots of apps this is very helpful. I didn't find gatekeeper helpful, all it did was prevent me from downloading apps from online. You can change this in the settings, but i think i am smart enough to know what to download and what not on the internet. This is a very solid upgrade and for the $19.99 price, it is worth the upgrade.
Pros The only thing I can say I really like is the ability to re-size windows from any edge. Auto save is a cool idea, though poorly implemented. Sharing everywhere may save a few key strokes.
Cons Most of the 200+ new features seem to be fixing things Apple ruined in Lion. Mostly I morn the loss of color. I react to the congealing blur of monochrome grey the same way most people react to fingernails scraped across a chalk board.
Summary After a week with Lion trying to restore the functionality I lost from Snow Leopard, I downgrade back and was happy for another year.
Mountain Lion is less of a disaster than Lion, but after a week with it, when I weigh the marginal value of new functionality against the angst I feel every time I have to distinguish between twenty or thirty grey on grey options, I decided it was less painful to go back to Show Leopard.
I have a minor dyslexia, which makes those grey on grey items in Finder or Mail all merge into each other, meaning I have to stop and think about what I used to do automatically.
Weighed this against the marginal functionality gain:
I really like being able to re-size windows from any edge.
The Notes and Reminders already existed on other apps, and I didn't find them useful there, or on my iPhone.
Auto save is a great idea, except when you didn't really want to save, when what you really want is "Save As..", or when you save that file to a different volume and all those versions are suddenly lost. Both Borland and Netware had much better, though less well known, versioning and auto save schemes 25 years ago, so this isn't new technology, and Apple's solution is inferior.
Auto restore, that is restarting applications and their windows is just the opposite of what I want, since the only time I shut down my laptop is when things go astray, and want I really want is everything shut down for a clean restart.
Notification Center seemed like a cool idea when it showed up on my iPhone, but in practice I never use it. Similarly, seemed like a good idea on the desktop, until I'm hosting a Webinar and notifications start popping up for everyone else to see. And why do I need my Emails in the notifications list when I have an Email application. Mucked with it though so Emails didn't show up as notifications, and I had to spend 2 hours trying to get unread mail count back in the icon on the dock.
Find fails in Mail if you are looking for something other than the first part of an Email address. Find in finder, I find to be far less intuitive than in Mountain Lion.
Saved finder searches from previous OS versions need to be recreated.
Airplay improvements, yes, but I still get better results using Airfoil.
Oh, and did I mention the lack of color. Is that icon greyed because it is not available, or is it just greyed. Can I click on the back button? Can't tell, it's greyed either way. The straw which broke my resolve was updating Aperture, an application all about color, only to find that all the color in the interface now grey. Grey is the new color. So why do I bother with this high resolution color display?
I could rant on for some time the things which Apple broke, but hopefully you get the gist here.
I evaluate an operating system the same way I do a pair shoes. Do I give up those well worn comfortable shoes for a pair of shiny, but stiff and uncomfortable new ones? Only if there is a significant productivity gain to the new which out weighs the comfort of the old.
As a play toy with some new tinker toys, the $19 may be worth it.
But without that productivity gain, the angst I feel in this new monochromatic world of Apple's, as compared to the sense of serenity I feel when using Snow Leopard, has caused me to revert, like I do with shoes, to the more comfortable of the two, Snow Leopard.
At some point my hardware will fail, and I'll be forced to make a decision to accept Apple's idea of a dumbed down monochromatic world, or maybe, if Apple keeps on this trajectory, I'll consider moving back to that other evil empire.
But I wouldn't recommend Mountain Lion if you have a choice.