I completely agree with Kerrie. I wouldnt be too worried about it at all! And as you said - he is already crawling and pulling himself up on things, which shows that he is definately on the right track.
Some babies don't even start walking until 18 months, yet that is not considered as abnormal.

I dont think my son started cruising until after 10 months himself... As I remember at his 10 month appt he had only just started bearing weight on his legs. Yet he took his first step at 12 months, and is now a confident walker.