Everyone probably remembers that Excitebike was a limited time free offer to celebrate the eShop's opening -- well at this point, there's probably a ton of fresh new XL owners out there, so you missed that promotion by a long shot.
If I could make a recommendation, it would be to pick it up if you can spare the coins -- Excitebike is a true classic, and the 3D effects, while minimal, add to the game's enjoyment for sure.
Fluidity is still available until August 19th, so grab it soon if you haven't already. After that point, Nintendo will switch it out with something else. In other Club Nintendo news, I just got my Gold Nunchuk in the mail -- that was fast!