My hesitance has mostly been my inability to verify the simulations. I prefer to have physical elements available so I can double-check the app. But I think I will have to resign myself to verifying against SPICE or something.
For me it's less about modeling the tube and more about checking the rest of the circuit around the tube if that makes sense. Does the tone control do what I want, and so on.
Personally I'm looking to verify relatively simple parameters of a tube in a circuit: gain, whether it's operating in the linear region given a particular bias, that sort of thing. If the model was simply a representation of the tube's characteristic curves that'd be good enough for my purposes.
So being SPICE-like would work ok. After all that's what I'm doing now!