I only have a little experience with tuning an ECU so far, but I think the thing that makes a lot of people balk at EFI on their classic isn't so much the tuning. It's the conversion.
The time and expense of putting together a high pressure return-style fuel system, plus building a well insulated loom and then assigning all the inputs/outputs in your ECU is pretty huge compared to installing a carburetor.
But I think it's like anything else, the more you do it the easier it becomes.