It's well worth the money. If you liked Wii Sports, you'll love this new version. It includes Golf and Bowling like the original, though they are greatly enhanced with better graphics and more sensitive controls. It also has Table Tennis, which was a Wii Play game, but again, it's been updated with better controls.
Some of the new sports are kinda dull, like Skydiving (your chute deploys automatically, so you can't try to intentionally face plant) and Basketball, which I just could not get the hang of. Wakeboarding and Power Cruising get old fairly quickly, though the multiplayer would probably be more fun. Archery was kinda fun, but the controls are a bit screwy; at times I'd be aiming off into space with the remote and still hit a bulls eye.
Frisbee Dog was kinda meh, but Frisbee Golf looks promising (I haven't actually tried that one yet.)
On the other hand, Cycling was both fun and a very good workout (you have to pump the remote and nunchuk to pump the pedals), and Canoeing was also a good workout, but occasionally suffered from crossed controls (rowing on the right would be read as if it were on the left, etc). Swordplay was rather fun as well, particularly Swordplay Showdown, where your goal is to hack your way through as many opponents as possible before your health runs out.
Island Flyover was by far the most interesting of the games; you pilot a small float plane around (and through) the island, popping balloons and searching for landmarks. As you locate landmarks and other secrets, you unlock new abilities. There's also a Dogfight mode, but I haven't tried it yet as it requires 2 players