Very nice laptop... Although I would go for ASUS over Lenovo for multi-media/gaming any day... I have that exact laptop but it is ASUS. I can run BO2/WoW/Aion/Tera/etc... you get the point. They run any game fairly well. So yes, it will run Runescape perfectly fine.
Gaming/high end multi-media laptops are great. Especially if they aren't that heavy/big. Mine is perfect for school and gaming. I lug it around everywhere. I also have a gaming desktop... I use this laptop more than that!