I'm "bi" when it comes to leading/trailing commas.

If I'm writing quick queries to grab data for someone or if I'm developing something and need to comment out columns, I use leading commas. Since most places I've ever worked either explicitly require trailing commas or have traditionally always used them (without written standards), I switch them to trailing once I'm settled on my design. Doesn't take long.

I don't have a strong preference either way, though I agree that leading commas are easier when you're developing code because they're easier to comment out. 🙂