Strengths: 300 plus horsepower and about 10 minutes to install.
Summary: I own APR's chip for an S4 I just sold. I put about 40K miles on the car with the chip installed and I had no issues. I purchased the chip with all four settings, stock/chipped/valet/race. If you are interested in buying it send me an e-mail at firstname.lastname@example.org
Strengths: Power enhancement throughout the RPM range
Weaknesses: none so far
Summary: I agree with Warren T's comments about the great improvements to the performance of the car. I have had the mod for 6,000 with no issues whatsoever, except for adding 1/2 quart of oil every 1,500 miles or so. You can cruise the freeway and never have to downshift to pass someone very quickly. The EMCS feature is not only good when you want to quickly switch back to stock for maintenance purposes, but I use it whenever I want a change of pace. Stock is fun because you use the gears more, then when you switch it back to modified, you appreciate the boost so much more. It keeps me from getting too used to the enhanced performance. I bought the spare ECU, which is why it's $995. Great improvements for the money.