I have an Asus UL50VT which is similar to the UL30a you are looking at (same processor) and it is plenty fast for what you are doing. Asus includes a desktop gadget that overclocks the Cpu to 1.7Ghz should you need/want to. If battery life is important to you, you'll love it. The switchable graphics is great; you get awesome battery life on the integrated Intel graphics but you are not limited to slow graphics.
It is very portable due to it's great battery life, thin profile, and it doesn't get near as hot on your lap as any other laptop I've every used. Plus that one is a 13 inch so it'll have an even smaller size than mine.
Antec 902 | Asus P7P55D | Intel Core i7 860 | Corsair H60 | 16GB Corsair 1600MHz DDR3 | Asus GTX 460 | WD Caviar Black 1TB & 640GB | Seasonic 620W | Windows 7 Professional x64