One of the things I love most about Panamax is how involved I am in every player's turn. This isn't a game where you can take your turn and then walk away for 15 minutes.
The heart of the game comes from loading cargo onto ships and moving the ships through the canal. When the ships exit the canal, every company that has cargo on the ship gets paid. In addition, if the ship is owned by a player company, the player gets a bonus. Not only are you allowed to load cargo onto other player's ships, the game mechanics strongly encourage you to do so. Furthermore, moving other players ships, either directly or indirectly, is frequent.
The Panama Canal is a series of locks broken up by two large lakes. Ships move into the locks which are then either flooded or drained to match the water level on the other side. This means that ships that enter the locks together must stay together until they reach open water again. It also means that ships can't enter locks that are already full until the ships ahead of them move out. The game simulates this by allowing players to group ships (up to a total length of 4) in open water areas and move them together using a single move. Once inside the locks, however, they can not be ungrouped until they reach open water again. So on my turn, I can group my ship with one of your ships and move them into a lock. You now have incentive to move the whole group, including my ship, further along on your turn. Furthermore, if a ship enters a lock that is already full, it will push the ships ahead of it into the next section, but you only pay the move cost of the first ship (or group of ships). This can lead to chain reactions where one move ends up pushing two or three other groups as well. At the end of each round (3 rounds of 4 turns each), you pay maintenance on each cargo you still have in the canal, with ships in the lakes paying the least and ships in the locks paying more depending on their position.
This leads to all kinds of interesting tactical decisions. Is it better to spend all of my movement pushing my ship along, or should I leave it in the first lock so that someone else has to push it out? Is it better to move my own ship, or to move my opponents ship from a low maintenance lake into a high maintenance lock? And this really just scratches the surface of the kinds of decisions you'll have to make.
If you enjoy medium-heavy games with a lot of moving parts that emphasize tactical decision making, you will more than get your money's worth out of Panamax.