I have Win8 on one of my work laptops. It's an Lenovo Twist (touchscreen).
My take is this. It's weird. It's as if in some sense it wants to be a tablet OS, and in another sense it wants to be normal Windows. You can either have the new Metro style, or you can have the traditional Windows style interface.
Having said that, even when you are in the traditional Windows style UI, things have changed. They have gotten rid of Window tool bar buttons. So, you don't have the minimize, maximize and close buttons on everything like you had in the past. Rather, you have to grab the window header and drag it all the way to the bottom of the screen. This in my opinion is a HUGE fail! You will find that it's more difficult to navigate at first. There is no "Start" button. However, you can go find Win8 add-ons. I did this immediately. Don't recall the name of the start button add-on that I found, it was free and very slick.
Regarding Sonar and Win8? Not sure really. I did load Sonar onto that computer, but I've not really done anything with it.
I have a co worker who said he hated Win8 at first, but forced himself to spend a weekend with it and now he loves it. Said it took some getting used to, but after getting used to it, says it makes sense. I'm personally thinking about making some significant upgrades to my home computer and when I do, most likely I'll put Windows 8 on it. It's quirky in my opinion, but I suspect that Microsoft will listen to the heat they have taken and address some of the issues.
Is it a MUST upgrade? Na, I wouldn't say so. Not from what I've seen. It is a shift though.