I have it and it's pretty cool. I like it better than Luigi's Mansion, but not as much as SMS.
A few levels are kind of like Luigi's Mansion. It seems they may have borrowed some sounds, music, and graphics from LM. But, in WW you can jump.
Some of the levels you have to do a pilldrive to get too seem like the levels from SMS where you where high up in the air. But, you can't fly or shot water.