Well I've got the original model like the OP, although when I bought it I didn't really realise it was designed only for use with 4 passengers plus me driving. So I squeezed in 5 to begin with, but after their friends saw how much fun we were having they hopped on board too. I desperately looked through the manual for tips on how to drive with 7 on-board besides myself, but there were only rules telling me to keep it to 4 passengers at a time! I resolved to try driving it so well anyway that I wouldn't get pulled over.
So anyway we drove for 18 months of normal gameplay spread out over 3 years, and while she was a good ride I found myself getting sick of complaints from the back seat about how things didn't quite seem to work with 7 rather than 4. Early on we upgraded to 3.5 mid journey and that led to a bumpy ride for a while! Didn't even bother going 3.5 with the DMG or MManual - after all it was only our first test drive!
One of the passengers stopped enjoying the ride and got off (she was only there to sit on her boyfriends lap after all) and I decided to park it. My friend has since jumped in the drivers seat and attempted to get things rolling again with a new road trip but crashed her with a TPK after session 1! And I thought I had trouble understanding the CR system as it related to 7 PC's... But things are up and running again with 6 passengers and it really is cramped compared to 4 plus a driver.
That's OK though because I've just preordered the new SUV 4.0 from Amazon, and its designed to transport huge numbers of people from the get go! So if my mate crashes the old beast again in the next few months and people no longer want him to be the sober driver, I'll have my new beast to drive them off in. And even if we never get going in the new vehicle, I'll enjoy looking under the hood, understanding all the nooks and crannies like only an experienced driver can.
Hell - I may even only take my girlfriend out for a spin, just the two of us, it looks like it can handle it. I just hope that the cup holders are the right size and theres a wiper on the rear window - I hate it when they miss out on those important little details.
Basically - I'm after a ride that is designed to handle any number of passengers that isn't a pain to drive once you've been going a while. Here's hoping the 4.0 model can deliver on its promise.