 I drove both new and used BMW's and Mercedes before I picked my 5-year-old S4 Cabrio.  Haven't regretted my choice for a second.  I think of this car as the "ultimate compromise." You can speed top-down through the sweepers of Big Sur in Summer or tackle the hills at Tahoe in the winter.  You can hoon it like a teenager, or ferry the kids to grandma's in safety and comfort.  And oh, the engine!  It's the finest engine I've ever owned - power and torque and an understated rumble.  It's hard to say how this car could be improved.  A hint: the 2005 tends to be ~$10k cheaper than face-lifted 06-09 models, even though it's almost exactly identical under the skin.