I imagine it would be. I'm pretty attached to my personal number - it's set up to be my date of birth (with the extra numbers, amazingly, giving my wife's DOB even though we hadn't met yet). So setting up a dedicated business number from the outset is a lesson I'll be taking on board.
This is a nice problem that Google Voice could solve today, since it lets you route calls; not to mention it has extra logic too involving days and time of day
It would be nice if you could have two Google Voice numbers, one personal and one business. This is because while GV has a lot of logic to allow you to route calls, if you don't already know the person who is calling, there is no way for GV to figure out if it's meant to be a business or personal call.
I'm not really into what Google Voice can do, but I've been wishing for so long that SIM cards could just aggregate n phone numbers, each one being like a separate inbox. And then you could just apply filters to turn off certain phone numbers based on day or hour...
Google Voice basically does the reverse of this; it provides a single "hub" number which you can configure to forward calls to N (I think up to 6) other phone numbers of yours. You can then setup rules for each phone number to not forward to your office phone outside of business hours, or to not forward to your mobile on the weekend, etc.
It's a lot easier for you to update everyone you know, and let the old business be your secretary rather than the reverse!