I haven't, but probably will eventually. I sink like a rock and never took swimming lessons, so the swimming portion has always kept me from entering.
If I was training to meet a specific time I would train the most in the area in which I have the most potential. For me it would be running. I can really improve my pace with regular training. However, if I wanted to shave a little time off my swimming pace, it would take loads of training.
Good luck, sounds fun.
Cut me, Mick.