Well, we rented it (my wife and I) and can't stop playing. I'd say the replay value is great, and by that I'd refer to the Score Mode. You can go head to head in all the mini games you unlock through Story Mode, then there is a ranking system and you can go online and compare scores with others by entering an internet code. We have had a blast with the games. I'd say borrow it but expect to get hooked.
As long as you enjoy head to head contests, the replay value on this is quite high.