You're right at my personal distance limit (about 600 miles) for any use of a personal plane for "must be there" travel. That's because I don't have an IFR ticket or a plane suitable for flight into known icing. Without both of those, I'd always need to be able to get there/home some other way in the event the weather turns bad. Since sometimes a walk-up airline ticket is not available at any price, my car is my backup plan, and 600 miles is about my limit for a one day drive. I'm not a fan of VFR over-the-top. For me, I'd only use it if I got into a situation where it was the "least bad" option, and I'd by kicking myself in the butt the whole time for letting that happen.