The 1720 isn’t half bad in games; best if you don’t get the high resolution screen though since as you up the resulution obviously it affects performance.
With the 1720 I could play CS:S at 1920×1200, with everything on High except shadows and shaders on low. If you bump it down to 1440×900 then it plays fine with everything on High; same for TF2 as well I believe.