>>Having done it both ways, I agree with both things you say. SET ENGINEBEHAVIOR is a hack, yes. And doing it right -- finding all the Group By clauses (trivial), changing as needed, and retesting -- can be substantial. It really depends on your future plans for the app. If it's going to still be around for a while, my tendency would be to bite the bullet and do it right.

I'd do it right also.
I've done several without the SET ENGINEBEHAVIOR and they went very well.
There were surprisingly few cases where changes were needed.
It sounds more daunting than it is.