The GPL license was a decision taken by my boss, not by me.
As a personal opinion, I agree with the license. I was payed to develop the code for a commercial product so it seems reasonably that the persons who payed me wish to profit from the money they invested on it. Commercial programmers can still use the code if they are willing to license it. It would certainly still be cheaper than to develop similar functionality from scratch.
As far as I'm concerned, I'm quite happy that I was allowed to share with a wider community the lessons I learned while working in this product. I think that they might be useful for many people, even if they are not allowed to use the code commercially.