The previous standalone BR player from Sony was the high-end BDP-S1 which retails at close to $1000. The S300 offers all of the functionality of the S1 in a much smaller profile, coming in at a size similar to normal DVD players, at almost half the price.
The S300 has the capability to play audio CDs, display picture CDs, video DVDs, and of course single and dual layer Blu-Ray movies. Audio visual capabilities include the ability to output a full 24-bit color (known as x.v.Color) 1080p FullHD signal at 24 frames per second. In non-tech speak these statistics mean that the S300 is able to display a movie in one of the closest possible ways to the actual video source maximizing picture clarity. When coupled with a television that can display a 24Hz signal (see Pioneer Elite PRO-1140HD) you are viewing the movie in the same way that it was filmed with no interpretation. On the audio side the most of the outputs desired by audiophiles is found. Uncompressed 7.1 digital audio, preprocessed 5.1 Dolby Digital, etc.
The full 1080p picture is only available when outputting through the HDMI output. DVD upconversion, up to 1080p resolution, is also only available through HDMI. When using component output the BR playback is limited to 720p, or 1080i, and no DVD upconversion is available.
Sony has also included their Bravia line of home theater synchronization technology in the S300. This allows for the television and supporting home theater equipment to detect the Blu-Ray player, and provides a streamlined interface and control through one remote control.