I originally bought my s4 with the intention of up-grading to an rs4 when my budget (and wife!) allowed, yet the more i spend on it the more i love the subtleness of the s4 as opposed to the outright aggression of the rs4. I plan to upgrade to ko4s when the 3s let go and aim to get to around 450bhp.
Unfortunately i'm doing about 28k miles a year, so its racking up more miles than i thought it would and longevity seems my latest worry.

I've still got about 3 years left of paying the loan off and just clocked 100k so fingers crossed it'll hold out! Would love to eventually keep it in the garage for weekend spins and tuning projects once it's paid for.
Mechancally it's been fine, although i've had my fair share of bad luck with the car

:side swipe by a skip wagon (off the road 13 weeks and £9k insurance damage); failed idler pulley tensioner causing the cams to seize 2 days after cam belt change (Audi replaced both cylinder heads under warranty at £? and off the road 5 weeks); hit a deer 2 weeks ago (still off the road and £3.5k insurance claim). Lost most of my no-claims now so might have to sell it anyway when i get my next insurance quote in!!
Anyway, i love the car, can't wait to get it back (before the xmas break PLEASE!), and fingers are crossed for a trouble-free-motoring 2007.