Outside of owning everything, of course! I picked up the PS4 on release night (through sheer luck on Amazon) and the other day landed the 8 GB Skylander's Wii U bundle for $220 at Toys R Us that my five year old had been asking for. (I also had a $50 GC, so only $180 out of pocket after taxes.)
I'm feeling very, very satisfied with this combo. I'm now covered to try the fantastic Wii U exclusives like Mario and Zelda, and get all the high-end goodness of the PS4 when I'm in the mood for that.
Now I just need to pick up the right set of Wii U games. Any suggesions outside the obvious Super Mario 3D World?