Don't forget - trisuits are unwelcome at time trials. Got to have some sleeves, so stick a lycra base layer (UnderArmour) underneath.
I went out sleeveless today as the weather was so nice, but it got me thinking - why do triathletes in this country go sleeveless? It was cold as hell during one part of my ride, more like the standard UK weather, so I conclude that slowtwitchers are nutcases. Can't be too hard to throw on something with a bit more arm protection in T1 surely?!?