Slow frame rate at times. Graphics & performance/details greatly suffer in multiplayer mode.
Hydro Thunder was an awesome game in the arcades for it's concept of powerboat racing, and Midway bought it home to N64 and did a great job with it. All the tracks from the arcade version return, as do the entire fleet of boats to race with, from the drag-racer inspired Tidal Blade to the humongous Tinytanic.
Controls are even better than in the arcade-quite responsive and you'll find tricks like jumping are easier now than in the arcade version. As is common with racing games, controls can be customized to your liking. The difficulty level is about right, but some hard challenges make you work to win.
Multiplayer is a lot of fun, but there are serious graphical issues. First up, a lot of the little details, like flames out of boosters when in use and obstacles along the tracks, totally disappear in multiplayer mode. Additionally, the frame rate slows down considerably and it's more difficult to see the course and other players.
If you're going to be generally playing by yourself, then buy this one if you were a big fan of the arcade game. If you want to play with others, it's better to take turns playing in single player because Multiplayer's just not worth it here.