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My personal philosophy is "never trust anything new".
The developers, especially Mithrandir, worked very hard on 2.2, and did a pretty good job, in my opinion.
But with anything new, whether it's software, hardware, or a new car, there's is always going to be the unexpected.
You should never upgrade to a new version without making a complete backup first, and making sure you know how to restore the backup if that becomes necessary.
In addition, you may want to test the upgrade first on a clone of your current installation, and exercising all the features to check for problems.
Also, it's a good idea to monitor the forums here, and the sf.net
bug tracker, to see if anyone else is experiencing problems.