I was working here in Vancouver as a sub-contractor for a company, until recently. I now started my own small company, and yes... have some of her clients! Yes.... I did sign a non-compete agreement.
I left due to the fact that I am much more the independant type, and I didn't like the way she ran her company. (an inconsistant functioning addict type, who had other legitimate avenues of income in addition to her business that no longer seemed to interest her)
I too debated whether or not to steal her clients. In the end, I decided to do it somewhat subtley. None of the clients were impressed at how the business was being run. Some of them knew I was leaving, and came with me, as I had gotten them results, and I was working with them directly, not her. I let the clients come to me. Some of the called me to see what was up, and I informed them I was now on my own. They followed of their own will, without me contacting them.
I think when you go against a non-compete agreement you have to be very careful about looking unprofessional, and "shady" in your industry. Depending on what industry you are in, I think that non-compete agreements don't hold up too well in court. There are so many grey areas... and complexities. If the clients come to you.... you cannot be held liable.
Be prepared to receive threats of court when your former boss finds out... but I have heard from someone who has been through it twice.. it usually doesn't go beyond lawyers sending threatening letters.
I'm not too worried about what will happen if my former company finds out that I "stole" the clients. I did not do it on a large scale, and hey..... I consider them more mine, as I am the one who put in lots of work and effort to keep them. In the end, they followed me for my skills and personality anyway.
It's every woman/man for her/hisself out there..... especially with the economic state right now. Grab what you can! Just be careful.....