I have a dedicated steel city mortiser. I use it occasionally but after investing in a Festool Domino, the use level is even less.
The laying out of a mortise is 75% of the work. Once laid out, I can use a chisel to cut the mart ice in very little time. It actually takes less time than setting up the mortiser. The actual cuts with the mortiser are fast but I have never been good enough to not require cleanup with a chisel.
I generally use mortiser and tennon joints very little. If I were building a lot of Shaker style pieces with large numbers of identical joints, the mortiser may make more sense.