I always tip for great service no matter where, but that's just me.
But a few times at the EWR UC, I did have no choice but to slap a bill to so much as get any attention from the bartenders, like as if tipping was a prerequisite before service. Despite that snafu, each drink I requested after that was poured swiftly despite how busy the bar was. Imagine that.
It isn't like EWR is the standard beacon for customer satisfaction by any stretch of the imagination. But when I approach any UC bar and slap a bill on the counter, good things always happen regardless of the bartender or the bar's capacity. Perhaps a good reference for PL.
I'd also imagine that any bonus, raise or promotion would go further than any tipping, so if it's in the UC or PL, do like me and write a compliment for them via the Customer Care site.