I would step up to the SB-600 as this flash unit has a turntable head.
So when you are shooting a portrait photograph (portrait as in aspect rather than person) you will be able to turn the flash head to bounce as it would if your camera was taking a Landscape shot.
That's the basics, but if you want to use a flash with a turntable head, you also get the benefit of bouncing light off of walls and ceilings to get a better effect.
Without this feature you are getting a fill flash while illuminates what ever is directly in front of the camera, and this can cause some bad shadows.
Also if you are concerned about the price you can get one used, from a shop or dealer.
Update,
after a new answer I though I should add imagesinfo to show how the swivel will help and is worth the extra, when using the camera in a portrait orientation, using this blog post by LearnMorePhoto.com
This is a shot with a straight on flash, notice how the shadow by the neck and lower hair makes it look like the hair is longer. This has happened as the light is blocked.
Now using a 90 deg bounce the shadow no longer exists and the background and face are more distinguishable. You will also see that the lighting is overall softer and the colours in the hair are more defined.