The blue LED is lit if the ESC is in the speed-limited mode.
I have the SS4300 motor, it's in "stock" mode all the time. It's not the fastest "stock"-motored car on the track, but it's always pretty good.
I bet that most of the people who complain about the 4300 motor running in stock class would stop complaining if they actually tried racing with one once.
They're not as fast as a "good" Monster ...but I could care less, since I don't have to work on it. Ever.