While I'm at it, I realized that it may be useful to further spread information about the problem that led to me fiddling with the latest IFs and JVM patches in the first place: the LS2J problems in 9.0.1 FP3. Specifically, it's borked. The main way most people have encountered this is via an exception dialog when attempting to add new plugins to an Update Site NSF, since that uses LS2J to accomplish its task - it displays several layers of stack and the upshot is that there's a java.lang.InternalError about calling a constructor.
The fix is to install the JVM patch from here; Interim Fix 3, while also worth an install, doesn't cover this.
There's another caveat about that, though, for those who have both Notes and Domino installed on the same machine. Since the installer for the JVM patch is the same for both, it will pick one of the two and not give you a choice to choose the other. In the case of the 64-bit patch (I don't know why it picks the client in that case), Ulrich Krause posted workaround steps. In my case, both were 32-bit, it found Domino first and not Notes, and the same commands didn't work. My ugly workaround was to fireup regedit, browse to (if I recall correctly) HKEY_LOCAL_MACHINE\SOFTWARE\IBM and rename the "Domino" folder/key to something else, run the installer, and then rename the folder/key back.