There have been a few early bug reports in 3.3.0, of varying degrees of seriousness. Most of these are now fixed. You can easily upgrade individual files from their respective bug reports, but if you prefer to fix them all at once you can now re-download the 3.3.0 package with all the fixes to-date included. Just grab it from the usual downloads page: http://kiwitrees.net/services/downloads/
If you have already grabbed the individual fix files don’t waste time with a complete re-install. It doesn’t contain anything else.