I'm starting to look for a replacement for my 03 x5 4.6is and I'm seriously considering the S4. Problem is I really don't know much about Audis, always been BMW fan, had few M3's before the X5. I'd like to get something with decent performance, practicality and awd for winter driving that's why I feel the s4 is really the only choice, the only things I'm not sure about is if I should get the present model or perhaps a new one is just around the corner? Also, sound system and electronics (navi, bluetooth) are important for me as I'm sick of BMW's ancient offerings. Another car I was considering was the new ML- it offers everything I'm looking for except performance and the MB's reliability is nothing to brag about so I'm kind of scared to go that way. Any advice, pointers? Thanks!

 

I got my 2005.5 a few months back. I really love it. The interior is high tech and comfortable, with Ricarro seats and Nappa leather. The power of the V8 is nice and even though the car is heavy, it is pretty fast. Handling is good and I like the ride. If you've had M3s, you definitely won't think it's a hard ride. The Audi is softer in general based on my limited exposure to Bimmers. To answer your points:

Stereo in mine is decent but not great. My A6's sound was much better, but it had premium sound and I don't think my S4 does.
NAV system is nice, though it is not touchscreen and punching in letters on a wheel is a little tedious.
Bluetooth is supposed to be a feature, but on the 05.5 they have to retrofit a module in the dash for around $1200.
Practicality? If you mean MPG, forget it. I get about 14 - 18mpg and the tank is small so the range is about 220 miles. Tne back seat has decent legroom for what it is - definitely better than the A4 of a few years back. Fitting 5 adults would be a stretch at best.
Not sure about reliability - it's early on for me. I have read some bad things about the clutch on sticks (mine is the tiptronic).

Hope this helps.