The AFR is brand new and offers more precise tuning than the S-AFC and also offers a response correction feature that eliminates the stumbling/running rich condition that is caused by aftermarket blowoff valves when using the stock MAF sensor (non-VPC). I'm not sure if you knew that info, or if you just wanted to know a first hand experience. I can get you a new one for $315. If you want more info on either of the units such as tuning increments, features, etc. email me at [email protected] or visit www.ExtremeAutosports.com
I have one and just began fiddling with it before I came back to London (Lance was never able to tune it for me, so I got a bit impatient). Anyhow, its easy to use, has tons of programmable points (16 if I remember correctly), and has a very wide range of programability (in comparison to others, if I remember correctly again).
Works great for me. Its also HKS - superior quality, blah, blah, blah. I know you've heard it all before. Dusty at MVP reccomended it to me.
It also has an orange readout on the LCD, if that matters.