I hear ya, regarding learning opportunities.

Within VB, I think VTable knowledge is interesting but not really as important, simply because VB does all that for you behind the scenes. And what VB doesn't do, TLBs can be used. But is nice to be able to dynamically create a functioning VTable and pass it to other code, i.e. APIs, and see that other code call back into your VTable. Playing with something like that, I was able to see that each time ObjPtr() was used, VB called QueryInterface before and after. I like playing with the low level stuff too -- more for curiosity and education than for actual use. However, with Windows moving more towards VTable-only interfaces since Vista, it doesn't hurt to know more about how they work.

Just for clarity. VTable-only means the interface does not support IDispatch, at least that's how I define it. IDispatch is what allows us to call methods via the object's reference and to use VB's CallByName().