Windows Phone is not flying off from the shelf as much as expected. Few ppl blame it on limited hardware like no dual core, limited memory, camera resolution etc. Few people blame it on limited number of applications and marketing.
Recently when I played with Nokia Lumia 710 I felt main reason is its Home screen interface. First people are very new to this kind of interface. They have never seen a phone with this kind of interface. Second reason is customization is very limited. Third reason is lack of aesthetics mainly at home screen. otherwise very few people will really care a phone has dual core processor or not. Although few people might like its minimal interface. But many feel it as plain and boring.
I feel it can be improved with following changes.