We have a big flat screen TV (Samsung LE46c650l1kxxu) in our conference room. Configuring it properly, we were encountering some issues.
This is a list of issues, providing a solution to each.

No sound with DVI/HDMI and separate audio

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There are some inputs on the side of the TV. These will not work for split video and audio.
On the back are more inputs you might not have seen. Choose HDMI/DVI as video in and Audio in for HDMI/DVI as audio in. Do not use RCA Show archive.org snapshot audio input but the TRS Show archive.org snapshot jack. The TV will recognize the input and play audio as it should.

Input lag (delay from mouse & keyboard interaction to displaying on the screen)

Activate Game mode from Settings, Generic

Overly sharp edges, especially on text

You can keep contrast high but should reduce the sharpness to a value around 10 to 20.

Save settings - settings automatically reset after 30 minutes or power-off/on

This behavior describes the 'shop-demo' mode. To make the TV remember your settings you have to set it to 'home-mode' once:

• On your TV, tab the volume up button once and then hold the menu button for some seconds.
• 'Standard' should appear on the TV. If you see a 'shop-demo' message, you're still in shop-demo mode.
• You can check, if you're in shop-demo mode by pressing the info button on your remote. If no 'shop-demo' message appears in the middle of the screen, you're not in shop-demo mode.