Worth every penny, especially for the TSA as others have said.
DUI when I was 19. Applied and approved for Global Entry and when I was 31. Obviously I disclosed it in my application, so perhaps thunderlounge was just saying to be honest and not omit anything. That was my last and only real offense, so I don't know where they draw the line. The first time I used it they pulled me aside (which I was told might happen), but after a quick conversation I went through and I've never had any sort of issue since.
It is true that if you have a checked bag you might end up having to wait for that anyway, but that's not an issue if just carrying on and I'd rather walk around the baggage area than wait in line with the normals any day of the week. In some airports there are separate customs lines for GE as well.
Lastly, you do not have to enter your known traveler # every time, and the only time you use the card is if you're driving back into the country. Global Entry is attached to your passport electronically. Go to kiosk and scan passport. You DO have to enter your known traveler # with each airline for TSA precheck. Assuming you have a login/profile with the airline (which you should), you can either proactively go in and add it to your profile or add it whenever you book your next flight. After that it's automatically attached to all your reservations.
I did it almost 4 years ago (think I have to renew soon), so I don't remember how long the processing took.