I think the question should be, why shouldn't you buy a Boxster? But which one? We need more information to speak to your question of this car being a good deal. The forum likes to suggest that you have it inspected by somebody who is a Porsche trained mechanic first. These cars can be very expensive to maintain.
Have you read this sticky yet?
http://986forum.com/forums/boxster-general-discussions/14685-thinking-buying-boxster-must-read.html