When booking have an option to book more than one service at a time with seperate date/times for each. This way the customer can see the total cost and pay for mutiple services at once if scheduling for something that is recurring. You already have this option under the extras tab, but not for the actual service.
This would alone, convert me to trafft, as its pretty crutial to be able to offer incentives for mutiple bookings. And for whatever reason 90% of booking apps dont have this, the ones that do dont work nearly as well and dont look as good as Trafft.