I totally agree with Rolf on his point about Trap and Spi downwind sailing. It's fine for a blast but as for the more important races it is quite a high risk option. Recently I have spent quite a few hours practicing getting out,in and gybing from the wire. In fact I'm starting to get a good routine together which certainly helps when the there is a need to go on the wire downwind during Club racing (which isn't often due to windward/leeward courses). However, at our recent Nationals I was not prepared to risk going out on the wire as any mistakes seem to be multiplied for some reason.
I get the feeling that in Australia wiring downwind is common place even during the big events and that is fine as long as you're rivals are doing the same as then everybody is taking the same level of risk but I'm certainly not going to trap in an Open Event unless somebody else can prove you sail as fast and lower than not trapezing.
To date my tacktick compass tells me that I'm usually sailing 5 degrees higher when on the wire and probably a little faster so every thing apart from the mistake factor seems about equal.