Use a segmented abrasive blade in the circular saw for cutting drywall

I wouldn't worry so much about blades flying out, even when using a cheap harbor freight saw. What is more likely to happen is the motor will burn out quicker than a quality tool. I've bought many harbor freight tools for "time to time" use. I've got a drill press that's lasted quite a long while ... granted I only use it a few times a year so I got my money's worth.

I think you'd be fine with the cheap saw as long as you're not going to use it all that often. The blade won't come flying out but the motor will probably burn out and fail long before the DeWalt motor would.

You should replace your blade when its dull. Ways to tell its dull:

• it starts binding
• it tears/chips the substance more than usual
• it burns the wood
• just a pain to use = a sharp blade should let you push the saw forward with minimum effort. If you find yourself forcing the saw forward (not ideal from a safety perspective), change the blade.