I updated my PocketBook Touch as soon as the RC firmware became available, and did not run into any problems since then except for a very minor bug in the Sudoku application. For the rest, only improvements!
The nature of a Release Candidate is that the maker of the software thinks this version is good enough for final release, but still wants to do some final testing. If no shocking issues come up PocketBook might well decide to promote this version 'as is' to be the final release. Or they might decide to fix some of these minor bugs that were found first, and perhaps do another RC. But in the end, the final release will hardly be different from the current RC. I don't think there is any risk in doing the upgrade now.
There are a few things to remember, though: the update will clear your history of read books on the Home page (although your reading progress will be kept for each book), and any custom themes you installed won't work anymore. These are probably not bugs, but just things that are that way, which means that the same thing will happen if you wait until the final release.
And if you really want to you can always re-install the 3.2 firmware.