Overall there is a noticeable improvement with the 550 in comparison to previous phones from the 500 series. The main problem which will be the same for all Lumia phones at this point is the lack of applications available in the store. It made it hard to review the phone as it is only as good as it's operating system. Once I got past the performance and camera stages there is not that much to test and do in comparison to what I normally have done on my other phones. Those applications are not available yet.