Actually ShellToys does seem to work in Opus, at least for me under Vista.
It's possible that on your system it has been "blocked" because at some point in the past it caused an exception. Opus will add context menu extensions to a black list automatically if they cause an exception.
Go into Preferences / Miscellaneous / Advanced and see if {2897079A-65DF-40E0-9711-892C3859EC3B} appears in the ignore_context_menus value - if so, ShellToys has been blocked. You can remove the GUID from this list and it should reappear - if so, maybe see if you can work out what caused it to be blocked in the first place so we can investigate the incompatibility.