I saw a G-Force motor Analyzer & it seems like a pretty cool and useful tool. Thing is, I heard that running the motor without load is a great way to blow up a rotor. So, is it worth it?

Just read the whole topic:
http://www.rctech.net/forum/radio-el...r-checker.html

Excessive speed on rotors might be a concern on modified motors, but not for the "normal" winds most people use. Anything from 13.5T on up is quite safe at no load. Just don't crank the timing to 60+ degrees!

I run a 17.5. But I do see the value of the motor analyzer.