[Disclaimer: OS X 10.8 Mountain Lion is a Developer Preview. It isn't even a public beta, which means that it's not for production use. It's not fully baked and you should expect anomalies. If you decide to dance with Apple's latest cat, only install it on a secondary Mac and only one one that's completely backed up. Expect to lose everything and factor in the time reformat and reinstall your HDD or SSD with a clean copy of Lion -- like I did.]
Disclaimers aside, Mountain Lion DP1 (see my first look), a.k.a. OS X 10.8, is actually a pretty compelling release. It unifies a lot of iOS features, has more social features, integrates iCloud at the Finder level, and comes with better security. But it's also a developer preview, so some features aren't fully implemented and some things are buggy -- as I discovered over the weekend.
Wanting to be up on Apple's latest release I installed Mountain Lion on my MacBook Air 11 which is my second/backup computer. My production computer is a MBA13 and I mostly use the MBA11 as a second machine for couch surfing, day trips, that kind of thing. It's mostly a clone of my MBA 13 but I save anything important to the cloud. That being said, it's the perfect development machine so I installed Mountain Lion on it last week.
I don't use my MBA11 all the time (maybe an hour per day and a few hours on the weekend) but my experience with ML so far has been decent. In fact, I was surprised about how many apps worked flawlessly in Mountain Lion. Example number one is the excellent 1Password from Agile Bits.
One of the biggest challenges with testing early, major OS releases is password management. Since I live on the cloud and use Web dashboards for just about everything 1Password is an integral part of my life. In prior OS X testing 1Password had a habit of not working (at least initially) which severely hampers my ability to log in to websites. With Mountain Lion, it just worked which made my life (and testing) much easier. Agile Bits said in a Tweet that it works because 1Password takes advantage of Apple's native extension APIs.
I was playing with Apple's latest kitty while I was upgrading the SSD in my MBA13 (more on that later) when things went south. I was using my favorite eBay client -- iSale -- and it was a little crashy. I'd write a little, quit (to force a save) then relaunch, do a little more editing and quit. This was working pretty well for a while but then the application started unexpectedly quitting more than was practical. I figured that I'd reboot to clean out the cobwebs.
And she never came back.
After restarting my MacBook hung on the grey Apple screen for what seemed an eternity. After waiting about 20 minutes I shut it down with the power button, waited and tried the same thing. Nada. Then I tried overnight. Nothing. I then ran Internet Recovery (Command-R at boot) and tried repairing the disk permission with Disk Utility but this hung (after fixing a few things) with the spinning wheel icon.
I couldn't re-install Mountain Lion from Internet Recovery because it couldn't see my WiFi network, so I was basically out of options. Faced with the prospect of losing my iSale document, I finally pulled the plug and elected to take the "nuke and pave" option. I ended up booting from my Lion flash drive, reformatting the SSD and re-installing the relatively stable Mac OS 10.7 (non-Mountain) Lion. Patching it up and calling it a day.
The lesson here is obvious, but worth repeating. They're called Developer Previews for a reason. ML DP1 is not production class and shouldn't be used as such. Only install it on a secondary, backup machine that doesn't contain any live data. And only if you can afford the time to reformat your drive and reinstall all your data. So even if your machine is a spare, time is precious and it also has a price.
That being said, I can't wait to test Developer Preview 2.