I think it's great and I haven't even played any of the Luigi stuff. I own it on Wii U and I highly recommend it. Not sure if it's ever been a lower price than that. I picked up Mario Tennis Aces since it's only $25.01.
I would say it's worth $38.88 if you haven't played the nearly identical wii-u version. The only additions for nsw are worthwhile if you want to make the game even easier (for kids, as an example).
It definitely gets cheaper physically though.
Thanks for the opinions! Yeah, I didn't get the Wii-U version so it'll be a brand new experience. I ended up getting it and I'm just waiting for it to finish downloading!