I have an '08 and I do like the new nav/idrive better. But, I doubt that is the reason you are buying the car and I would not make it an important issue. If the nav/idrive is that important, you might be looking at the wrong car.
I would look for something with low mileage and something that still has a warranty, or an aftermarket warranty available. It is simply insurance, these cars are incredible, but if the DCT breaks, I suspect it is $15-20K. I think the M3s are really tough, but I would avoid one with a lot of track time, etc. I do not think the occasional track day and autocrosses are any concern. I have seen instructors/students at the performance center just beat these things to death, and they just keep ticking. The instructors with 3riders doing launch after launch, smokin the tires/drifting through every corner and the cars just keep going (with frequent tire replacements).
I like mine with virtually all options, my only "regret" was the rear shade...., chincy. I don't think any options are "bad". I think the DCT is important to have. It is great to drive and the automatic function is nearly as good as a real automatic.
The performance package might be important to wannabe racers. The truth is that 99.99% of us will never fully utilize the capability of the car with or without the performance package. I would not turn one down, I think the wheels are nice and the minimal lowering probably looks good. I believe someone said Top Gear thought it was not as good as the regular ECD.
I am not sure about the ECD, so will leave it to others. I do think it adds a lot to the car and I would not want one without it.
Good luck, you will love the car.