HELL YEAH I'D USE THIS. Assuming, though, that I'd have a normal lifespan and not be due to get hit by a bus or something in a year from now or not die of some illness or something.
Honestly, I feel like I'd rather have a slightly shorter life in favour of being totally comfortable in my own body. And I don't feel there's anything vain about going out of your way to make yourself how you want to look. So yeah sure, please do go ahead and take a year or two away to fix the things I feel are my biggest flaws! I'd have slightly fewer years to work with but I'd be living them more happily because of this. I don't think I'd use it to fix more than two or three things, but I'd definitely use it.