I've got an SZ140P10. I haven't seen any reviews of the SZ240 specifically, but from what I know about them, it's just a SKU refresh, and has the option for a 120GB HD versus the 100GB max on the SZ140's.
It weighs about 4lbs, and I've never been happier with a notebook weight. My previous notebook was a BX565, a 15.4" 6.2lb notebook that feels like a brick compared to this light thing.
As for casual gaming, the NVIDIA 7400 in it should do fine for light gaming, or even the latest games, but just don't expect all the settings to be turned way way up. It'll be modest to low settings for the card, but you'll still get great performance out of it.