The guys at FierceDeveloper have put together this nifty chart showing the top smartphone operating systems by number of active users in the United States in October, based on comScore’s data. The following chart is based on a list that is derived from a three-month average ending in October of U.S. mobile subscribers over the age of 13. ComScore asked respondents what type of phone they own, and derived operating system information based on those responses.

Below: the chart of comScore’s data. The yellow bars are the most recent statistics.

What’s interesting about comScore’s latest number is it’s the first time iPhone OS market share has surpassed Windows Mobile. According to the data, approximately 36 million Americans are smartphone owners, with 40% of those owning Blackberries and 25% owning iPhones. Windows Mobile share has shrunk to 20% and with the increasing popularity of the iPhone and Google’s Android OS, it’s not looking too hot for WinMo (Windows Mobile).

What is your personal favorite? What OS would you prefer for your Business Smartphone? Windows Mobile, Apple iPhone or Google Android (maye be Nexus One)?

Microsoft has already announced that the first Windows phones, identified by the fact that they are running Windows Mobile 6.5, will be made available at retail stores worldwide on October 6, 2009. Microsoft is underlining that version 6.5 of its mobile operating system brings an improved user interface and that the Internet Explorer Mobile browser includes a new engine as well as built-in Adobe Flash Lite support.

Google’s Android 1.6 Donut has support for CDMA radios, QVGA and WVGA resolutions. Android 1.6 also brings Quick Search Box for Android which is fundamentally universal search that searches locally on your phone and through the internet at the same time, new text-to-speech APIs, and the beautiful new Android Market. The camera’s interface has also been updated with improvement to the camera’s loading time (approx. 39% faster), and a neat battery usage indicator that details which applications are using the most power. One of the most striking advancements is the introduction of CDMA support in the telephony stack which will open the door for Android phones to launch on Verizon and Sprint. Under the hood, Android’s Linux kernel has undergone a boost from version 2.6.27 to version 2.6.29, the most important smartphone-related change being the introduction of Intel’s open source WiMAX stack and drivers.

On the other hand, Palm has also launched a new update, version 1.2 of WebOS. One of the most remarkable advancements in this update is support for LinkedIn in the Palm Synergy synchronization service. Palm has also added the ability for users to input a credit card number in the App Catalog program, indicating that commercial software could be ariving soon. Quick Search, like Google Android 1.6 Search, isn’t something iPhone supports at the moment, but is something we hope Apple must be looking into if they need a way to survive the competition. Palm announced the release in an entry on the company’s official blog. A more detailed overview of the enhancements can be found in the release notes.

Being a smartphone user, which OS would you prefer? Google Android Donut 1.6, Palm WebOS 1.2, Windows Mobile 6.5 or the mighty iPhone?