Just got these in today. Went for a short 5 miler in them. Very similar to the Kinvara 3. They feel slightly roomier in the forefoot. The heel collar is definitely lower than the Kinvara 3, but I was never bothered by the heel collar height in the 3's anyway. One difference I did notice almost immediately once I started running is that they aren't as firm as the Kinvara 3, making them slightly less responsive (might be the PowerGrid as opposed to the ProGrid used in the 3's). Overall they felt good and familiar (I've put a ton of miles on Kinvara 3's). I'm looking forward to putting some miles on these and I'll report back when I have.