Not so crazy -- if you have IBIS models on all components, and you're licensed for the Signal Integrity module (which I think comes default, maybe it's not ever done separately), just run it and you're good!
Read the official Altium documentation for use.
Some constraints:
- Impedance only works over a plane. You need to use planes, not signal layers with polygons, for ground references.
- It doesn't check if the planes are split (AFAIK). You shouldn't be running traces over splits anyway (note, splits in a single layer are fine, as long as there's a contiguous plane nearby in the stackup).
- It only works for traces, and assumes all traces are transmission line structures.
- I don't recall if it does crosstalk.
- If you have cables between boards, say; well, if IBIS models support that sort of thing, and you can synthesize a model of the cable, then you're good; I'm guessing not, though?
- If we're talking fast (fractional ns edge) signals, FR-4 loss is a factor, which, I don't know if it can model it or what. Keep this in mind when targeting eye diagrams.
Tim