Station Wagon's aren't supposed to be gorgeous, but this one is. Over 1 month of ownership, I've received more stares and random compliments on this Avant than I did in 6 years of owning an S4.
Ibis white with blacked out accents (Titanium package) makes for a stunning combination amongst a sea of beige family sedan's.
While only a packing a turbo 4 cyl (200hp) the A4 strikes a reasonable balance between punch and fuel economy. There's plenty of power for overtaking, yet it still returns hwy mileage in the 30's. An available manual transmission adds to the fun.
The Avant configuration provides plenty of space for hauling gear, without the handling penalties of a tall SUV. Once inside, you'd be hard pressed to guess that you were in anything besides an entry level luxo-sedan. Handling is good with the sport suspension, though it's admittedly hauling around 3800lbs. Still, it never feels ponderous nor uncomfortable. Composed yet relaxed is a more apt description.
Mechanically there are some known weak points (coil packs, cam follower, PCV setup) but the aftermarket has a number of solutions, and in some cases, Audi has extended the factory warranty on these items.
In all, if you're looking for a fun to drive, good looking, well optioned, comfortable family hauler that won't break the bank...it's worth your time to check out the 2006-2008 Audi sedan's and wagon's.

Over 6 years and 100000 km's, not a day passed that I didn't look forward to getting in my S4. Power, comfort and confident all-weather capability all in one package.
While it's definitely a high-maintenance vehicle (budget $2K for annual maintenance and repairs), mine never once left me stranded. I did experience excessive wear of Tie-Rods and Wheels Bearings.
Fuel mileage around town averaged 13L/100km's, but on the highway I routinely saw <8.5L/100km's (at 110km/h).
Dry road handling was very good and the suspension remained composed on all but the worst surfaces. Winter performance was mind-blowing with a good set of winter tires. The most confidence inspiring car for foul-weather commutes, Quattro lives up to it's reputation.
While plenty potent in stock form, the platform responds well to modifications. A chip (remapped ECU) and lowering springs really spice things up.
I wouldn't hesitate to recommend an S4 to someone, assuming that they're prepared to deal with the required maintenance.