It's actually a deal compared to the 250g slim console.
That Extra $100 is worth it and here's why
Limited Edition comes with:
A copy of Mw3
2 custom Mw3 controllers both with swivel D-pads and plug and play charge kits (i know you can buy those separate but it's better than one)
A custom slim xbox
320gb hard drive
And It makes sounds from CoD when you eject the disk and power the console on.
So now i get to Jizz every time i turn on my xbox
Now I believe all of that is worth the extra $100