Check you Cakewalk Command Center for the latest update. 

Just started Sonar Platinum and yes it is much quicker now to start with the new start screen. 

Yes, confirmed on my least powerful system John.

So soon! This is going to be fun.

Been there, done that, waiting for my t-shirt..........

Has anyone noticed a smoother Sonar with this update? It seems to me that its performance is better. 

It does seem snappy. Gotta like that.

John,
I was working with it last night and DID notice SP to be snappier.. Also seemed a lot smoother even than the IPSWICH version.  Was doing a rough mix for a client and had to transfer the files from an old version of Sonar. 
Copied all the tracks over, renamed the tracks and got to work adding Aux files (instead of using busses).
Was REALLY nice how fast things got to moving and the rough mix was done in a couple of hours. 
Also like that the Smart Screen doesn't come back up after I close the file (speeds up things) but I key bound it to the letter S so that I can recall it when/if I need it.
So far so good!  Cake, I like it!!!

I am in the camp of liking the Start Screen to reappear. However I fully understand the wish for those that don't want it. I find it very handy. Now that it is much quicker it is acting very well indeed. 
 
They did something to the internals of Sonar that to me equals better performance. Yes they have another winner on their hands.  

I hear you John.  I like the Smart Screen as well.  I also like that it's more "controllable"...
They should put toggle in the preferences section so that you can turn it on or off like the original quick list had.
 
As for the internals..  Yes, if they equal better performance, I'm all for it!