One of the problems with windowsill growing is that plants are going to grow toward the window. So I put some lights on top and along the sides to help even things out a bit. It's not ideal, but it works. Also, the light helps during dark CT winters.
One thing I'll say about my windowsill experience... it's a lot of work. Things will dry out more quickly or slowly depending on the humidity, I have to adjust the blinds with the seasons and the hours (e.g., in the winter when the afternoon light comes in at an angle, it can heat things up quickly), I adjust the window opening with the weather, I must contrive various things to keep pots that face the window from overheating (e.g., styrofoam), and so on. But it works for me because I like tending to my plants daily.