While I can definately see the attraction of Stik's description of competition aeros, and do not wish to take anything away from that, the artificially limited form of aeros seen in competitions isn't necessarily the be-all-and-end-all of aeros, and I'd like to defend those sunday morning skyhole-borers.
Barrel rolls, rarely seen in competition aeros, can be the amongst the most satisfying (if, admittedly, somewhat basic) manoevres to fly, and are easily within the capabilities of even basic aerobatic mounts. While I can well understand the need for a small aerobatic box for judging competition aerobatics, one of the main attractions of flying to me is the freedom it offers, and I'm not a massive fan of the concept of this imposed restriction.
As has been mentioned before, flying even a few basic manoevres would give many PPL holders more confidence in their aeroplanes, hopefully avoiding the affliction whereby people are scared to use greater then 20 degrees AoB in the circuit, as well as a better feel for the stall boundary.
As I said before, I wouldn't dream of not aknowledging the amazing aerial ballet performed in competition style aeros (indeed, I plan to try my hand at it soon), but I'd also hope that the participants in such also respect aeros performed outside this environment. I have the luxury of flying aeros on a regular basis in a relatively high performance aeroplane as part of my day job, as well as in a variety of powered and unpowered machines in my spare time, and I enjoy each activity in its own right.