I've spent thousands of $ for mics, pre's, A/D, computer, and plug-ins. I still don't use a control surface, and I came from an analog console. For me, the mouse is the easiest and most accurate way I can tweak. No longer do I mix directly with faders as much as I do with incoming signal and output of the final plug-in on any given channel. I also don't Automate using faders much anymore, either.
A control surface is nice, but they can't control everything on your screen, and you're forced to still use a mouse. Plus, and I'll agree with bitflipper, if the control surface isn't a great one, (in my opinion, a FULL 32+ channel console), it's going to get in the way. I haven't liked any of them I've tried, except the big $60,000 AVID consoles, and I still don't like a track-ball.
More, if you have issues with Sonar, issues between Sonar and the console, or simply issues with the console, I think you'd be literally throwing it off the desk and grabbing the mouse.
So, if you've come from a console, and really miss it, I'd shop for a GOOD control surface, and learn it inside-out. Work out any kinks, and keep sailing. For me, I'm happy spending the money elsewhere. I simply can't justify the money for a decent control surface.