My partner and I recently undertook the Mumbai-Civitavecchia leg of Costa Allegra's repositioning cruise. This was our first time on a cruise ship, and we booked it because some friends were doing the full Singapore-Civitavecchia trip and suggested we join them, and because the itinerary was very appealing.
Prior to making our booking we had heard little of Costa or the Allegra, and after reading some of the reviews on this site we wondered what we had done. Our friends, though, had sailed on the Allegra previously, and kept telling us to expect a 3 star ship, and we would be happy. It was good advice.
We travelled to Mumbai independently, and spent a couple of days there prior to embarking. What a fascinating, almost overwhelming city.