This site has some interesting details on mobile video cards: Notebookcheck: Computer Games on Laptop Graphic Cards . Please keep in mind, this information could differ if your laptop's CPU is bottlenecking video performance. The Intel 4500, as previously stated, is just horrible for games.

If you haven't purchased a laptop yet, I strongly recommend this one: Newegg.com - ASUS K50 Series K50AB-X2A NoteBook AMD Turion X2 RM-75(2.20GHz) 15.6" 4GB Memory 320GB HDD 5400rpm DVD Super Multi ATI Mobility Radeon HD 4570 - Laptops / Notebooks . It doesn't have mind blowing speed, but it is a "balanced" system. The reason I post it is because even though it won't play the latest and greatest games, it is still a much more powerful GPU than what the DV6t offers at the same price point.

The graphics card is dedicated with video that should perform at twice the speed of ATI's onboard 4200 graphics, and probably several times faster than the Intel solution. What you're sacrificing here is a slightly slower CPU since it is a hybrid of AMD's older K8 and K10 architecture. In other words, it runs at the speed of the older architecture (that's been used since 2006) but makes use of the newer Phenom style power saving. Not to mention it already comes with 4 GB of memory as well as a 320 GB hard drive which is more than sufficient for most laptop users.