Spray-Foam Insulation Project

I have a project I want to insulate using that spray-foam stuff. You know, the stuff that looks kinda like “Great Stuff” but you spray it on a whole wall, attic, etc to form an airtight layer of insulating foam. You can buy kits online and I’m wondering if any of you have any experience using the stuff. If so, what are your thoughts, experiences, results, etc.