Going by Baez's Graphics Performance list the X4500 is just above a 6600gt and HD 2400 Pro. While those cards aren't exactly top of the line I doubt anyone would consider them underpowered for a non gaming system.
I have a 5lb 14" laptop and I wouldn't consider it small by any means.
Small light laptop are one of those things that are difficult to appreciate until you have owned one. I have used my 2.3lb netbook more in 10 months than I used my larger laptop in 2.5 years and I would never go back to anything larger than a 13".
As I mentioned before size isn't the Lenovo's only advantage, it has overall better hardware in addition to better battery life and superior build quality.