I got my Wii since launch, and I got my PS3 last summer together with MGS4.
They both complement each other very well. The Wii gives me Nintendo games (Mario, Zelda, Metroid, ...) and the rare 3rd party gem (No More Heroes, de Blob, Mad World, ...). My PS3 gives me HD goodness (since when is being a graphics whore bad?), awesome games (Dead Space, RE5, Mirror's Edge, ...), a good and free online service, Blu-ray...
I wouldn't want to get rid of either, but I can't deny how my Wii is my least played console of this generation. And I would've gotten a 360 instead of my PS3 if it weren't for MGS4, free online and Blu-ray.