The New PS Store Design is currently avialable in the UK, Australia and will be coming to North America on 23rd October 2012.
UPDATE: Sony has pushed back the date of release of the new Store in North America. No new release date has yet been announced.
Personally, I love the new design it looks great! Far more attractive than the old PS Store and now I just hope Sony are planning to update the XMB Bar. What do you think?