I've got one combo unit- the fusion X. It is slow, but does a good job washing. I offer two friction washes and two touch free washes on the menu. The other bay has a Water Wizard 2.0 which is of course all touch free. The fusion X is in the closest bay to the street and does slightly more revenue than the WW. However, a good many of the customers still purchase the touch free options ( I'm guessing 30%). As a result, the majority of washes sold on this site are still touch free. I can check some number on a typical period if this info interests anyone.
I have not had a lot of perception problems, but there are occasional customers who see the brushes and drive to the other one.
As you can imagine, the machine is much more complex than a touch free only unit. However, I will say of the combos I have seen the Fusion X offers a genuine quality touch free wash that rivals the water wizard and other good gantry units. It profiles the car and the oscillating nozzles do a good job of impingement on the surface of the vehicle. I will the put the touch free wash quality up against any inverted L I have seen to date and I think it will come out a winner. I have seen other combos that offer a half-assed touch free option. Then you hear the the owners of these machines complain that no one is using the touch free options. If the operator is serious about offering a quality touch free wash and the combo unit is capable of providing one I think it a combo is possibly a good decision.
Another related thought is I have seen several operators get a bit lazy with their touch free unit's chemicals when a friction unit is also on site and begin to offer a sub-par touch free wash. They develop a philosophy of "if it's not cleaning good enough, take it through the friction wash" I could envision this same problem developing with the owner of a combo unit. I think if that philosophy is adapted you will eventually see the touch free options used very little.