XBMC
OpenElec
Optimising
Turn off the RSS feed in System => Settings => Appearance.
To ensure your Raspberry Pi can keep up in fast moving complex scenes you need to set the refresh rate of your monitor to match that of the video. To achieve this head over to System => Settings => Videos => Playback and set Adjust display refresh rate to match video to Always. Now fast moving scenes will play without glitches or stuttering because XBMC no longer has to pull up the refresh rate to 50 or 60 Hz.The only downside is the slightly increased chance of interference patterns. But these are still far less annoying than shocking movement in scenes.
Add ons
Bluetooth
lsusb - shows you if the device is there
Bus 001 Device 007: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
bluetoothctl - opens a control panel to help play with your bluetooth device. Use help for commands.
list - lists the controller show - shows the statusses scan on - scans for devices devices - shows you the devices it has found
you can also use hcitool - it has a few more options
hcitool scan
rebooting a LOT helps a lot on the pi!
LiveTV
The system needs to be running Tvheadend which takes the input from a DVB card and moves it to XBMC Live TV. It's configured through a web interface. In the Howto's there's a section on Ziggo that may apply to UPC as well.
DVB
DVB-C = cable DVB-S or S2 = satellite DVB-T or T2 = terrestrial
A list of linux (and therefore XBMC compatible) hardware is to be found on the LinuxTV wiki
Standard you need a DVB-C card with a CI interface. Some DVB-T boxen also have DVB-C compatibility and a CI card.
The HDHomeRun with TVHeadEnd is your best bet, but unfortunately this is not CI+ certified. So far, nothing is, as CI+ was developed to stop people from watching TV on their PCs.
You can find a list of raspberry pi verified peripherals at here