I remember WizooVerb - it stopped working properly (W5 version) around N4 release with a workaround (use in a 5.0 config). Unless I am wrong though there is no Win 7 64 version.
SIR2 is worth getting because you can build up stereo or even true stereo sets from separate IR WAV files. I wish this were possible in REVerence - would be a killer feature (along with an expanding IR library of course).
@drorh4 - you cannot open AltiVerb IR in any other plugin, likewise Waves IR-1 & IR-360 files.