I use the VIX as a confirmation tool. The VIX is derived from options prices, so its a completely different market.
Say if ES prices were trending up and the VIX did not reflect that by moving down, it would definitely be a cause for caution for me.
I would probably not trade and prefer to wait for a better setup.
Also if the VIX is near its high or low for the day, I will ignore any trading signals to the opposite side. I've gotten burned many times by jumping on false breakouts that were not confirmed by the VIX.