"In the past two years we've concentrated on making the mobile phone a good camera. Now we're doing the same for music." - Mike Pauwels, Senior Global Product Manager.
512MB is probably not all that much space to store MP3s on and this storage is dwarfed by the kinds of capacities seen in recent iPod offerings. However, the company will initially market the W800 as a phone that one can transfer their music collection onto, rather than hold in entirety.
The company says it is committed to supporting open standards in music - i.e. MP3 and AAC rather than Sony's proprietary ATRAC 3 format. However, this isn't the case for memory cards. Sony's proprietary Memory Stick is the only type of flash storage you'll be using with the W800.