I have built, and used a computerised touch screen cue system. Provided you use a decent touch screen, they are great. The thing is the screen needs to be mounted in the correct position. What I did, and it worked well, was also made a hardware interface as well. It had certain advantages. Because the place I designed and built it for did not do conventional shows and a lot were based on timing, we decided it was the best way to go. The interface basically had 2 buttons. Cue Standby, and Cue Go along with a keypad to advance cues etc. Each cue contained a list which lights needed lighting and a delay number for staggering cues. The hardware interface was just straigh toggle switches.
I have also seen one systems that were basically analagous to a cue light system. That defeats the entire purpose of a digital system.
A properly designed digital system, where there is a need for one, can be a life saver. Things like placing control of other systems within the prompt desk can make life so much easier - they are not there to clutter things up, but in an emergency you can bring them up. For example when I have speced venues, we have always put a simple control in for the lights Sure, lighting control may be hidden away (under the program I wrote, System>Lighting>On Stage System) but when it is needed, it is there).
I suppose the question is, when they do it, will they do it properly.