I tried it twice and twice I nearly burnt out. Luckily, after the second time, my business was making me a good living already, so I never looked back.
The problem is that consulting will take a lot more time out of your life than even a regular job. His clients sound professional and fairly large, but the majority of your clients will be small and mid-sized companies. They will try to nickle-and-dime you for everything because they want to save money.
You only have so much mental energy and I found that I didn't have much left over to work on the business. On top of this, you then needed to worry about chasing down customers for payment, which adds to the stress.
I also worked for a consulting company (they grew like what is described here). It was very difficult for them to find reliable consultants. We went through so many different people, I was the only one that was still there after a year, when I finally left.
It's a brutally difficult business and will sidetrack you to the point where your other business may not ever succeed.