Hi All:
FWIW....here is what the Sprint 650 manual has to say about the little green/gray arrows and mine does seem to follow what the manual describes:
"Appears with gray arrows when your device is on and connected to the
Sprint PCS Vision network. You can still receive calls. Appears with green
arrows when your device is connected to the Sprint PCS Vision network
and a data session is active (for example, when you are browsing the
Web). You cannot receive calls."
SteveTaz