The X1a runs Windows Mobile 6, not the most modern nor exciting mobile operating system out there. Having said that, there are two good reasons to take a look at the X1a. The first is the hot arc-slider design. The three-inch screen slides up and out to reveal a full keyboard. Throw in a sleek metal body and the X1a looks great. Secondly, Sony Ericsson has done its best to cover up Windows Mobile with an interface based on Panels, task- or application-specific components that can be configured, added or deleted to match the user’s preference. The X1a will be available in the Spring for $699, without a contract.