The Holideck lounge at T4 is very nice, and I was happy to hand over my Priority Pass card for access. Decent food and drink, and a couple of quiet areas if it's not too crowded. Overall ^ .
The Priority Pass bumph says there are two lounges at BOM - neither has a shower, though, and 'free drinks are limited to one per person'

. Look for the Clipper lounge at International Terminal IIA or the Club lounge at Internatinal Terminal IIC.