Hi Adam,
The one that you've linked to is the "nifty fifty" that you'll have heard so much about.
As above, it's a great little lens for the price and its large aperture really comes into its own if you're shooting in low light, if you want shallow DoF or if you need to get a fast shutter speed in medium lighting conditions without resorting to flash.
However, for the requirements that you've stated I notice that you already have the 18-55mm lens in your camera bag.
If it's the IS version I'd absolutely echo the sentiments above about its close up ability. It's not a macro lens, but it does have a very short minimum focus distance which means that you can experiment with close-up photography to see if it's your thing - that's something that you won't get from the 50mm.
As far as portraits go, if you're not finding that lacking a larger aperture is limiting your photography then perhaps the 50mm isn't for you. You can shoot at that focal length with your current kit lens, and although it's not quite as sharp as the 50mm I'd find it difficult to recommend the 50mm as a complementary lens on sharpness alone.