Software evolves, interfaces change. If software companies adopted a policy of never changing interfaces then we'd still be clumping around in Windows 3.1. Every now and then there's going to be a major overhaul of the software you use. It doesn't happen often, but when it does it's going to piss some people off. There is simply no way around that.
You have to realize that Cakewalk has many different users to cater for. Longtime users are always going to insist that their prolonged loyalty to the product should be Cake's first and foremost consideration and that making changes they don't like is a "kick in the face." The reality is that Cakewalk would not be able to financially justify maintaining the product if "longtime users" were their only customer. They must continually attract new users. Not just refugees from other DAW's but also complete newbies who have never used one before. Without these customers you would not have Sonar. To attract new customers and compete with other DAW's you have to rethink, redesign, improve, overhaul, innovate.
I've been through all the changes to Windows, Microsoft Office, Quickbooks, Adobe products etc. Each time it provokes a litany of angry complaints. I don't like the way this works now, I can't find this feature, I miss this shortcut. Sometimes you just have to take a day to relearn a new design. But people don't bother doing that, they figure they're confident enough to stumble around in the dark and work it out themselves. In the process they miss new shortcuts and new features which have been designed to make things even easier than they were.
Be honest - since the introduction of the Skylight interface, have you ever sat down and watched an up to date video course? Why not sit through the whole Groove3 course? You might well have more than one "aha" moment.