Sterling,

I had run flats on my Mini Cooper S and it was like driving a shopping car...at high speeds. The ride improved 1,000 percent after going to traditional tires.

My X5 also came with run flats and, while it's not quite as brutal as the Mini as far as ride, after 500 miles I made the decision to change to Michelin Latitude HPs (non-run flats). While I only have 400 miles on them, I drove the same route I had driven on the run flats, and again discovered a very marked improvement.

So then comes the issue of the spare. Well, first runflats aren't perfect...while at the BMW dealership I saw not one but two different BMW's arrive on a flat bed. The service manager said that both had run flats and they "shredded" -- so they were left stranded anyway.

I don't have a 3rd seat, but while I'll eventually source a spare rim for long trips, I've got a can of "tire seal" along with a great plug in portable tire inflator - both of which hid nicely in the side compartment on the left when your looking in the trunk. My AAA membership includes up to a 250 mile tow. While it's not a perfect solution, I've only had 3 punctures in 30 years of driving, and two of them had no air leakage at all.

It's a tough call, but that's the route I'm going.