I've had my MS for over 3 years and 50k miles. Like others, I've noticed how much less fatigued I am at the end of a long trip. Today I drove from Phoenix to San Diego, but did it in a virtually new gas car, so it was an interesting comparison. I was noticeably more tired at the end, even considering I shared the driving. However, it got me thinking -- how much does the air suspension play a role? I drove an Infiniti QX70 today, using cruise control much of the way, and it is probably very good in terms of noise/vibration. However, it does have a coil suspension. Thoughts?