I flashed Denmark ROM on my GB CV Black 930 and now am rocking Denim.
Here is what I've felt and seen in last 1 hour since Denim:
1) It seems faster (had to say that!)
2) It seems smoother
3) Haven't seen a single loading screen (jumped between Messenger, Skype, Calendar, Settings and Cortana)
4) Camera images are sharper and feels like they capture more details.
5) LOVE the long press of camera buttons when inside camera! It does these smart images that is essentially a video but you can view it frame by frame and choose a photo of your liking. Excellent stuff for peeps with babies, sport fans and those who take photos of objects that are still for microseconds.
6) Hey Cortana! - refuses to calibrate no matter what. Everything with Cortana works but you have to calibrate Cortana so that only your voice will wake her up and no one else can do that. But my Cortana doesn't even know I am trying to say "Hey Cortana!" - anyone got lucky?
7) Screen colours are nice to look at now. No needs to toggle any display settings like in Cyan.
What did you feel about Denim, if you have it now? Let's do our first impressions and beat Rubino on the front page, shall we?