I've flown to mine, but I've thought about driving (actually, I've thought about taking the Harley, but I know that would wear me out). The advantages of driving would be that you could keep your bike with you the whole time; you'd have your car in town for obvious needs; and you could drive the course if you so desired. But flying is so much faster and I think flying takes less out of you. However, bike + airlines = major hassle! You may have sometime to drive, but OMG, 12-15 in the car would just drain me, and coming home would be terrible. Could you split it up in two days out/two days back?

You and I have similar options: Boston/Logan & Dallas/FW means you have good airline and time options. You could fly from Logan to Chicago/Midway, rent a car, or fly direct to Milwauke, rent a car, but then you have to contend with the bike box (I assume you are flying with the bike which is a whole 'nother topic). You could also take a small turbo prop from Chicago or Milwaukee into Madison which is what I did. I rented a car for IM Wisconsin, but for IM CDA I took a shuttle, used my bike for transportation, and bummed a ride to/from the race site. FWIW, Madison is a 'small' town (compared to Boston) and the locals are very knowledgable Ironman fans, so if have have shaved legs in Madison the week of the race, everyone assumes you are competing. I guess my point is that I don't feel that having your own car is absolutely necessary.

As I noted earlier, how are you getting your bike there? Your bike transport may also factor into your decision. If you are using a bike transport service, then flying might be more logical since you won't have to mess with your bike. If you fly with it, you'll have to rent something big enough for a bike or get a shuttle van or minivan cab. But if you really, REALLY want to keep your bike with you the whole time, then driving may be better. Also, if you drive your own car, you'll miss out on walking through security, getting dinged at the metal detector, and saying, "Oh, yeah, I forgot TO TAKE OFF MY IRONMAN FINISHER'S MEDAL."

I have driven to ones about 7-8 hours away, and it is fine for me as long as I go early enough that my legs have time to stretch out -- they do get a bit tight with time in the car. The drive home is tougher (nice to have someone else to drive, but you still have to deal with not moving your legs for a while and then trying to stand to walk to the bathroom!)

Like many tri/body things, this will depend on your body and how well it handles car travel. Airlines (as TriSooner said) are faster, but more hassle. Cars are slower, but more convenient and can be easier for bike transport.

I've always driven to IMLP from The DC area...9 to 12 hours depending on traffic and coal trucks...usually faster up than back when I make frequent stops to stretch and eat! I've driven to run Ultras as far away as 18 hours. It's just so much easier, I think, to pack up the car and drive than schlep all that business to the airport and you have a way to get around once you're there. Leave plenty of time before the event and take your time comin' home and I think you'll be fine.
I'm imagining a Harley...with a bike rack.

I drive to IMLP and few years back from NJ and it took me over 23 hours(traffic and accidents) in a straight shot. I arrived on Thursday Morning.
I only stopped to gas up, pee, and grab coffee.
I was a little overloaded on caffeine and jittery when I arrived but I was able to stretch and get rested enough in the few days before the IM.

I was glad to have all my tri stuff with me in the car and at the time gas prices were cheaper than airfare and shipping my bike.

As always thx for everyone input; I guess driving doesn't sound bad. I always drive an hour to my 70.3 and back with zero issues...I'm leaning toward driving