Yes, it apparently is intended to work in Office 2003 + 2007, though I had mistakenly thought the thing only worked in Office 2007, as above:
...it seems to have only been developed for Office 2007.
However, you may not necessarily be right when you say:
Other than that, it certainly is buggy.
- because it's working fine in my Office 2007 now, as per my post above:
So, I suspect that something was blocking the Add-In from working and CCleaner removed the blockage.
What I mean is, maybe it's the system configuration that is causing the problem, rather than a bug in the OfficeTab Add-In - though equally true I suppose is that it could be a mixture of both!