With internal storage of 130MB, and no memory card supplied, you'll be looking to buy a Memory Stick Micro (M2) card sooner rather than later if you're taking plenty of photos or want to use the music or video player to any great extent. Cards up to 16GB are supported.
The card slot is positioned under the rear shell, on the side, so you have to remove it (but not the battery) to swap cards.
Assisted GPS in the C903 which works with a selection of pre-loaded applications. It's not quite as quick to get a satellite fix as recent Nokias, such as the E75 or 5800 XpressMusic.
The ubiquitous Google Maps app provides location finding, route planning and search facilities from the handset – using cellsite info to help define area locations quickly and download updated mapping or search information over the air. It's not full Sat Nav but is an extremely useful extra to have on a phone
For a more rounded Sat Nav experience, Wayfinder software is pre-loaded. You can get step-by-step mapping instructions for walking or driving routes, searches for numerous locations, with over the air updates of maps, including 2D or 3D views, with signals and guidance as you go along and overviews of planned routes.
This works reasonably well, and is responsive to movement but again requires a mobile internet connection for regular updates, so might not be so reliable if you're in a remote, cellsite-light area
It's not as slick or intuitive as a typical large-screened in-car Sat Nav set-up and isn't designed to be a replacement for a standalone system. It is a useful app for a mid-range phone though.
Sony Ericsson has also linked the A-GPS to a fitness application, Tracker, which monitors and computes information from training runs to work out your performance. Again, it may not replace dedicated kit for serious running enthusiasts, but it's a clever, fun application for GPS that casual runners may like to use to track routes, speeds and so on.
Another application, NearMe, is a Sony Ericsson app that provides location-based search data under a variety of categories near to your current location.