Wow Johnny_V was wrong on every point.
The system menu is still version 3.3, the whole 3.2/3.3/3.4 is the version of the system menu, not of the update in general. This update didn't contain a new system menu at all, it just adds IOS51 and fixed the signing bug in all other version of IOS. For future reference, call it the IOS51 update.
Downgrade is possible with system menu 3.3 if you have not installed the IOS51 update (seeing as downgrader has nothing to do with the system menu this makes sense). I'm not entirely sure why, but apparently it isn't possible to downgrade even if you have cIOS installed and installed the IOS51 update, apparently the downgrader uses another IOS (probably uses IOS36 for something).
Final point, this update was not just about VC piracy, it blocks the installation of any unsigned code onto the Wii. This includes the hombrew channel, starfall. custom IOS versions, etc. This greatly cripples hombrew in general. For the most part, the only people that this didn't cripple were the pirates who had a custom IOS (that contains the signing bug) installed.
This patch was probably in the making since the previous one (where they removed the signing bug from IOS30 and IOS31). They would have to check to make sure that removing the signing bug from the old IOS versions wouldn't cause any compatibility issues. People who think that this was targeted to block VC piracy or to stop WiiGator's backuplauncher are wrong, Nintendo released this patch to fix a known bug with the Wii (and a major security flaw), and as a result homebrew was crippled.
Marcan and crew already have an exploit that will work with the newest update which they plan to use to install BootMii, but they haven't released any details, and they haven't released any hombrew applications that make use of this exploit yet.