As far as I can see from the changelog, all the bugs in 2.2 have been resolved. Looking at the changelog and roadmap (and this is my personal opinion) I wouldn't be surprised if version 2.2 was skipped in favour of a release of 2.3 - but don't quote me on that.
To answer your other question, I've been using the 2.2RC3 release for a while without problems but (as always in these circumstances) your mileage may vary.
If you ask these questions on the EFW mailing list you may get an answer from one of the developers.
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