Ideapad is good for casual gaming. It has integrated graphics so dont expect anything high end, but HD4000 is quiet good card with support for latest technologies like DirectX 11, OpenGL 4.0, Shader model 5.0 and OpenCL 1.1.
The GPU Speed is 650 Mhz by default but just like the i5 main processor gets turbo boost up to 3.1 ghz, it also goes up to 1.1 Ghz as the load increases. Memory communications happen at 800 Mhz. So technology support wise it is as good as any new generation card and performance wise it will probably match up with previous generation discreet graphics cards. New games should run fine on Low-Medium settings and a bit old games run on Full settings.
I personally play Quake 3 Arena, Unreal Tournament 2004, Doom 3, Need for Speed Most Wanted, Need for Speed Undercover, Max Payne 2, Harry Potter and Half Blood Prince, GTA San Andreas and Prince of Persia Sands of Time on FULL settings with resolution set to 1366x768 and get flawless performance. Mine is a G-580, but apart from the metal upper body versus all plastic body, these two machines are identical.
It all comes down to your individual needs. I am very well satisfied with my machine, although I do wish that I would've spent 4k more to get the Z-580 with better build quality. G-580 is also good and the plastic used is very high quality and somewhat scratch resistant, but it is after all, plastic
