They are quick to explain that the X10 isn't optimized for multi-touch. Therefore, it will basically only have pinch-to-zoom capability. Sony Ericsson explains that "some brilliant engineers actually [were] able to change the driver and firmware for the touch digitizer to make some multi touch gestures work." Their multi-touch is a work in progress, and they only plan to enable it in the web browser and in Google Maps.
There is support in 3rd part apps, but you can expect some erratic behavior. For example, when the fingers cross each other on the X or Y axis, the X10 might react in a number of inaccurate ways. The video below shows multi-touch benchmarks, as well as their multi-touch solution working relatively well on Angry Birds. While we aren't exactly thrilled about such a partial solution, we commend them for heeding the customers' concerns.
source: Sony Ericsson via AndroidGuys