In practical terms, any time the LED is always on or off, there is a serious problem. If the LED is blinking, then Salvo is at least running, and therefore usually the rest of the code as well. A blinking blue LED is very soothing.
Example: my UART was getting flooded with noise on the RX line. The LED was not blinking, so this was a clue that the PIC was so busy doing something (in this case spending all it's time looping through the ISR) that Salvo was getting no OSTicks.
Example: I was having conflicts with multiple devices on the SPI bus, and the PIC was stuck in a 2 instruction loop waiting for the BF flag (which was never going to be set). The LED was always on, alerting me that something was seriously wrong.
I've been using Salvo on PIC 18's for almost a year now, and it works great. I have very limited memory resources but I wanted a product with source access and strong technical support. Salvo is the clear winner for my products.