I'm currently in an E92 M3, and am about to put my order in for an F80 M3... however, the ATS-V has the potential to have me change my mind. Cadillac's got a few things going for them here. Styling is of course subjective, but exterior styling is Best in class for the ATS-V. I'm not crazy about the interior - because I prefer the more horizontal dash layouts to Cadillac's more 'vertical' style, but again, that's subjective.
For the drive... Look's like Cadillac brought the power, and the ATS is well known to be a better drive than the 3 series. Now the M3 is a pretty big jump up from the base 3 series, especially this time around with the rear suspension directly bolted to the chassis, but I'm pretty optimistic on the ATS-V.
The things that bother me: Yes, it's CUE and other tech stuff. I haven't done a point-by-point comparo, but BMW looks to offer a lot more here. A lot of this stuff seems petty on a performance car, but it's going to be my daily driver too, and this is the stuff you interact with the most.
Most egregious failure: the gauge cluster. Again, it seems petty, but you'll look at it all the time. Has NO business in a car like this. It looks like somebody found an instructables on how to hack a 1 x 4" screen into the gauges from a 98 Silverado with a dremel. Cadillac should be embarrassed here. To me, it's not even completely below this kind of car, but it is one of the worst looking panels in any car today. There are economy cars with better looking gauge clusters. Just so, so bad.
Most of all, the pricing. It's just too close to the M3's pricing, for a car that just doesn't look like it delivers as much. The crappy gauges and CUE are going to make it sting to think I could have BMW's much nicer interior to interact with every day. Maybe the car drives enough better to nullify that - we'll have to wait and see. I think, if you want to dethrone the king, you need to offer the same for less money, or for this kind of money, a lot more product.
I predict the real thing that will kill this is the dealers. I live in Houston, so for one, discounts will be rare (although M3s can be found discounted already). These GM dealers will smell blood and charge a market adjustment for sure. Most will probably try to talk me out of ordering (even though I'm super particular) because "we've got a great CTS right here...". Their desperation to have me drive off in a new vehicle that day - and pay a premium for it will be depressing.
But it's such a great looking car, and looks to be such a great drive... I'm hanging in there until I know otherwise.