Notebookcheck.net has an extensive list of games benchmarked on HD4000
that you can look at (HD4000 is row 210). The saving grace here is that laptop only has a resolution of 1366x768 which will work in favor of the IGP. As others have said, don't expect this thing to crank 60fps at high detail settings in demanding games like Crysis 2 or BF3. This is NOT a hardcore gamer's laptop. There are many games that can be played smoothly on it though. It really gets down to the games that you typically play. There are 2012 games that don't require much graphics horsepower at all to play and older games are obviously less taxing.
Look at the benefits also. A laptop with integrated graphics will use less power than a laptop with a discrete card. That generally means longer battery life if all other things are equal (they rarely are, especially between brands, but it's a rule of thumb). Not having discrete graphics allows for a slimmer profile, less weight, and lowers the price.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 120 GB Vertex 3 Max IOPS, 2 TB Samsung EcoGreen F4, 8GB 1600MHz G.Skill @1.25V, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Samsung SSHD, 8GB 1866MHz G.Skill, Hand-Built Wood Case