According to reports from multiple sources, the HTC Desire S is currently receiving an update to Android 2.3.5, which also bumps the mid-range handset from HTC Sense 2.1 right up to Sense 3.0. The new version of Sense, which first shipped on the Sensation earlier in the year, features a redesigned 3D launcher and lock screen setup, amongst other enhancements.
Apparently unbranded Desire S owners in the UK, as well as owners of Vodafone T-Mobile, O2 and Orange have begun to see the update roll out to their handsets over the past few days. To see if you're in line for the update yet, head to Menu -> Settings -> About phone -> Software update. If you're not seeing anything just yet, then hold tight, it'll probably be sent out sooner rather than later.