First of all - it's not 100% unproblematic... but here are the experiences I've had with the upgrade today (just now).
As expected, the download took a while, I guess I wasn't the only one who downloaded it ;-) After the download (of approx. 4.5 GB), the installation is started. The first step up to the reboot is pretty quick, about 1-2 minutes - but then it takes - depending on the computer - between 30 minutes and 2 hours. The computer then restarts and the settings etc are applied without any problems. The VNC access also worked without any problems - I was able to do a Mountain-Lion update remotely.
After the start, you immediately get the message which apps are no longer working: this includes the OmniBar in Safari and the Lion server extensions. Neither is bad, because OmniBar is integrated in the new Safari and the server extensions weren't that useful for me anyway. However: if you need OSX server functions: stay away from Mountain Lion for the moment!
Then an update is necessary, new versions of IWork are installed and FinalCut etc.
XCode 4.4 will also be installed with the upgrade - will be important later.
I use the Mac as a development computer and need Java as the system. Here is a summary of what happened:
- After installing Moutain lion, the Oracle JDK 1.7 is no longer available, it can't be found in the command line: Solution: I downloaded Java from Sun again and installed it - but it wasn't running yet. The Java settings didn't help either. Important: If you have set the environment variable JAVA_HOME, it somehow doesn't work in the console. After deleting the JAVA_HOME variable or setting it to the correct path, everything worked as desired (/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/)
- GIT no longer works - executable is gone! This is of course annoying and should actually be installed without any problems via the downloads in the XCode settings (Command-Line tools). Unfortunately I can't download the tools from my place - my AppleID is not valid for it, for whatever reason?!?? A little googling and you will find a download link that works - now GIT also works
Addendum: now the download of the command-line tools in XCode also works. However, if you don't want to install XCode or don't have a developer ID, you can download it separately.
- IntelliJ works fine except for the above issues after fixing them
- mongoD works fine
- Gmail is better supported now but for some reason there are always problems with password verification - strangely only in calendar, not in mail?!?!?
- Hyperdock no longer shows full-screen apps in the small preview...Addendum: Hyperdock has been updated, now it works again and brings a few new features!
- VMWare Fusion is no longer running - I hope there will be an update soon - Addendum: VMware Fusion is running, but Parallels Desktop 6 is no longer - Ok - I switched to VMWare anyway, so no problem for me.
- Tunnelblick doesn't work anymore - OpenVPN-Connect only worked after I reinstalled it (somewhere understandable, if you think about it) - Addendum: Tunnelblick works better with the current beta (3.3 Beta 12) - GateKeeper complains neither - unfortunately the "original" OpenVPN software (openvpnconnect 1.8.3) doesn't really work stably in Mountain Lion. I uninstalled it and only use Tunnelblick (it's prettier anyway)
- The web share can no longer be found under the settings. You now have to start Apache manually in the terminal sudo apachectl start/stop/restart or something like that. It's also missing the per-user config /etc/apache/users/XXX.conf. You can reconfigure everything. But it doesn't really bother you... unless you're a mouse pusher ;-)
- Google Docs no longer works completely in Safari 6 (spreadsheet is stuck) and in Chrome(!) not even the start page works anymore! Must therefore use Firefox
If I notice anything else, I'll post it here - Have fun with Mountain Lion!
Oh yes - software update is now launching the App Store!