One of the hottest ROMs for the SE Xperia at the moment is Touch-IT Leo 4.2 by itje – one of the most prominent ROM chefs for the Xperia X1. The ROM is a mix of the Xperia, Windows Mobile 6.5 and the latest incarnation of the interface Touchflo 3D from the upcoming device HTC Leo. Head over to HTCPedia.com to grab your copy. Bare in mind that the ROM is built around beta firmware, so don’t be surprised if it’s a bit unstable. If you’re unsure of how to flash a custom ROM, check out the Guide to Windows Mobile.
Update: Touch-IT Xperience v14, another excellent ROM for the Xperia.