Definitely no cons - I've done it 3 times on the Island and will be doing it for the 4th time this November on the Coral. Have also done a trans canal.
If you book the Ferry shore excursion, you'll be taken all the way over to the Pacific Ocean through the other 2 locks so it's just as good as a trans canal ... better cuz you don't have to do a long plane ride. Plus you get an entirely different perspective of the locks from the ferry. I'm not big on shore excursions but I continue to rave about this one.