In my experience over the past 20 years, the part of the cue the operator is actually listening to is "LX", "Sound", "Automation", "Tab", etc, and the cue number is the least of the worry.
What you should be carefull is that your cue titles don't watch up like "Lights" and "Leaves" - that, in my experience, can be a problem.
But, in the end, I think it's a matter of style. I just haven't dealt with a designer or show that has lettered anythings in about six years. So, I would avoid it - I also don't like things like Cue Q . . . and it would bother me to skip over the cue letter. Thus, I just stick to numbers for LX, Sound, Projections - and call automation by the piece moving. But that's my style.