Forbes has a detailed report on the S60 platform:
There are certain advantages for developers as well who have turned to the S60. Developers of mobile content say that it allows them to create content for a wide variety of handsets at a reduced cost. Kansas City, Mo.-based Handmark, which aggregates content and develops and publishes wireless content, says that it ordinarily has to do more than 17 “builds” to support 20 different phones. Those are costly and time consuming. However, by using the S60 platform, it can do six “builds” to support 50 phones. That means quicker time to market and lower cost.