A survey shows that smartphone makers have to fight hard to hold on to increasingly fickle customers, with 75% of smartphone users intending to change Mobile operating system when they upgrade.

The survey, conducted by GfK, found that only a quarter of smartphone users intended to stay with the same OS when they made their next smartphone purchase. And as many as 56 percent of smartphone users didn't know what handset they would buy next time around.

Somewhat surprisingly, given the early success of the Microsoft Windows Phone 7 OS, only 21 percent of those with Microsoft Windows Mobile OS-based devices said they would be upgrading to a Windows Phone 7 handset. By way of a contrast 59 percent of Apple iPhone owners intend to stay with Apple - perhaps because of the locked-in nature of the iTunes eco-system.

Ryan Garner, the lead analyst of the survey, told PC Pro: "People are really keeping their options open. There's been an explosion of new choices in the market over the last year, with Android and Windows Phone 7, and with new versions of Symbian, the RIM OS and Meego in the pipeline there is huge choice."

GfK surveyed 2,653 mobile phone users in Britain, the US, Brazil, Germany, Spain and China.

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