Mountain Lion, Apple’s latest version of OS X, is currently in beta. However, it is in a stable enough form that some journalists were given sneak peeks over the past few days. I’ve been working with the OS for most of the last week and weekend and, as a public service announcement, I’d like to state that while Mountain Lion is a compelling upgrade to OS X it’s not currently ready for prime time.

To be fair, the worst version of OS X I ever used was an early build of Lion. This build essentially rendered my machine useless and made me cry uncontrollably when my Time Machine backups failed. Never, as they say, again.

However, being a glutton for punishment, I gave Mountain Lion a spin.

Mountain Lion installed without a hitch on a 2010 vintage MacBook Air although it refused to install on a 2006 Mac Pro – a disappointment that still burns a little. I know this old workhorse is six years old and more than capable. I’m sure there will be a fix down the line but right now there is no way to get it to install.

The OS has “grey screened” once and my install was marred by a system failure that required, literally, about 24 hours to fix. I didn’t have to sit there the whole time to fix it, but apparently one install froze, the machine locked up, and the secondary install process required a massive download. This took most of a day and night.

The most interesting improvement is the Notifications system. Not unlike Growl, Notifications sit unobtrusively in the corner for a moment and then disappear. There is a new icon in the upper right corner, next to the search glass, that allows you to see recent notifications. Growl still works fine as do most of my apps. I only noticed that QuicKeys, a text macro app, failed for the first few hours of use and then magically started up when I reset the machine.

Messages is arguably abysmal, with two odd UIs clashing with each other wildly. When you look at messages, you mostly see the huge message window. However, there is also a smaller buddy window that is a clone of iChat. I’ve also had trouble syncing my conversations across devices. I would love to be able to receive, for example, iMessages that appear on my phone on the desktop and reply from either device. As it stands, the service is focused around an iMessage email address. I’d love it to work with phone numbers as well.

Mail is improved slightly as well, with a new “star” system for important messages and a VIP system for important senders. For example, you can set Mom or the significant other to a VIP and then only receive a notification when a VIP emails. MacWorld has a wildly complete look at Mail, but there’s not much different that anyone would notice except that the new Mail does not support RSS feeds.

Twitter integration worked quite well as did page sharing in Safari.

As for behind the scenes I noticed that Mountain Lion was as stable as Lion and, barring the rare catastrophic shutdown, I’m working as quickly and as efficiently on ML as I was on Lion. I never experienced Gatekeeper’s security system during my time with the OS.

Would I recommend that non-devs upgrade right now, just to “kick the tires?” Assuming you have access to a beta – for whatever reason – I’d say no. I’ve seen a number of bloggers and other tech-types mentioning they we’re upgrading but generally it’s not worth the potential headache and the agony of waiting 24 hours to see if your MBA was totally hosed thanks to an install error was enough to make me want to revert to Lion. However, Apple sent this out as a pre-release for a reason. It works quite well and the new features are actually mostly apps rather then baked-in improvements. Don’t pull the trigger yet. It’s fun to experiment but it’s also fun to have a computer that works.