How good is an Intel® Graphics Media Accelerator X4500 for gaming?

Ummm..... it sucks.

Intel's current graphics core, the Intel HD 3000, in certain Sandy Bridge Core i3/i5/i7 CPUs is actually pretty decent and is actually slightly faster than a desktop Radeon HD 5450. It's no fire breather, but certainly better than the GMA X4500.

The slower Intel HD 2000 graphics core is found in the "lower end" Sandy Bridge Core i3/i5/i7 CPUs.

On a scale I will rate cards mentioned as follows:

-Intel HD 3000 = 105% performance of the Radeon HD 5450.
-Radeon HD 5450 = 100% performance of the Radeon HD 5450 (wow that was a hard one to figure out).
-Intel HD 2000 = ~75% performance of the Radeon HD 5450.
-Intel GMA X4500 = less than 50% performance of the Radeon HD 5450.