I loved Starfox 64. I thought it was awesome.
But playing Assault now is way, way, waaay less impressive now than playing Star Fox 64 was back in 1996 (or was it 97) on the N64.
Basically if you're a Star Fox fan then yes, this game is definately worth getting, but it could've been much better, especially for a freaking 2005 game.
PS you should know I'm an extremely critical and tough person when it comes to games, heck I thought Wind Waker, Half-life 2, and even No One Lives Forever 2 were disappointing and not as good as they should have been, although I acknowledge they were among the best of 2003, 2004, and 2002 respectively... But yeah you probably shouldn't listen to me too much... I'm sure you'll have a great time with this game. Although, yeah, it could have been way better.