We did the Panama Canal Partial Transit Tour shore excursion on our Princess Cruise.
Pros: 1) I highly recommend this tour if doing a cruise so that you can see the canal from both the big cruise ship AND from a smaller boat; the perspective is totally different and amazing. 2) There were adequate restrooms. 3) You will drive through Panama City briefly on the way to Colon back to your ship, so you will see at least parts of both cities which I enjoyed.
Cons: 1) The included lunch was NOT good and quite light, especially considering the long length of the tour. Bring food from the ship if you can. 2) The boat is essentially not air-conditioned--there's a small indoor area that has a small a/c but it reduces the 105 degree outside temps to probably about 85 degrees....this is not actual air conditioning. This made the 6-hour tour very uncomfortable. Additionally you couldn't really see the scenery from the indoor area because the glass was very foggy/old.
OVERALL: I would recommend that you do the tour but 1) be prepared to be HOT, 2) bring a book for some of the down-time when you go to cool down in the sorta-A/C area, and 3) bring some snacks from the ship. If you use a wheelchair, you may wish to check with them to see how much of the ship you can access.
Visited November 2013