Dave Scott, the king of Ironmen, was a vegan during his entire reign over the Ironman scene. There's a lot of validity to the vegan diet and I've considered it myself. It would be hard for me with a wife and kids in the house though.
That's actually kind of where I got started with the idea...I had read that he was vegetarian throughout all 6 of his Ironman victories and wondered why the heck any athelete would want to have that kind of diet lol. Then I read about Brenden Brazier, another triathelete, having a completely vegan diet and had a book out with a real menu that hit all the nutritional points, so I picked it up and played with some recipes (I've discovered over the past couple of years that I have massive food allergies, so I'm always looking for new, "safe" meals to try). They actually tasted pretty good and gave me a TON of energy.
His book has a rotating menu that goes for 12 weeks, or 3 months, with multiple meals a day, cooking information, and shopping information, and it's not bogus vegetarian stuff, if you know what I mean. Since it gave me a lot of energy, I've decided to try it for the full 3 months. I'm still experimenting with recipes here and there to make sure I know how to "cook" everything, which is why I figure I'll try it more towards the end of the year once I've gotten a handle on creating meals with some of the weirder foods. Fortunately I live right next to a Whole Foods store, so getting fresh ingredients is pretty easy.
I am married (no kids yet), but my wife won't be doing the vegan program with me, so I'm on my own for this one

I don't have any plans on doing it beyond that 3 months, just interested in trying it to see what happens. One of my hobbies is grilling, so I'm sure I'll be anxious to get back to that asap

I was really into triathlons for awhile, before I found out the running part didn't really work for me because I have a trick knee, but I liked having the energy from the veggie-based foods so I thought I'd give it a shot!