I've had a Bugaboo Frog for about 5 years now and LOVE IT. Worth every red-hot penny. We've taken it to Hawaii and gone over lava fields (baby stayed asleep), I've taken it for jogs on the beach, it maneuvers around the mall like nobody's business, and it has stood the test of time. No creaks, squeaks, or shimmies.
That said, I do drive an Expedition so generally speaking I don't have to dismantle it or fold it to put it in the car. However, when I drive my husband's car I do take the seat off and fold it up. It is no worse than the Graco travel system (we had one of those originally and it fell apart after 6 months... ugh!)
The only thing that I really don't like about it is that it doesn't come with a cup holder (sort of like buying a BMW, lol! Where the heck am I supposed to put my Starbucks, people?!). I would recommend buying a cup holder to go with it.
If trunk space is really a big issue for you, maybe check out the Bugaboo Bee. It's a bit smaller and folds one-handed. I'm not sure if it comes with all the bells and whistles of the Frog though.