I think Sirius's advice to Harry about how the world isn't split up into good people and Death Eaters applies a lot to Draco. Draco is very similar to Snape in that both characters had an unhealthy fascination with the Dark Arts, and both realized they got in too deep when they saw the true horrors of being on Voldemort's side. Draco is a product of his upbringing - a father who was rich, spoiled, and wanted power at any cost, and a mother who is snotty and pampered. Dumbledore saw the good in Draco on the tower, and realized he is not a killer and only doing it out of fear. Like someone else said, Draco also was reluctant to identify the trio, because he knew that would mean death for them. But he also wanted his family to be powerful again, so he considered turning Harry over to Voldemort for praise, and also for his own safety because the war would stop.

So long story short, I think he has both good and bad qualities (mostly bad) and has shown both cowardice and bravery, which has made him an interesting character. Like how I feel about Snape, I think Draco is actually more interesting than Harry (who is always good) and Voldemort (who is always bad).