Be warned, make sure you ask for a by-pass (I think that's what it is called) to be fitted on the rear of the STB (so you can still get terrestrial through an aerial, not a brilliant signal though).
Other than that, more channels, the box is bigger, good picture quality and on screen menus (may or not work reliably). Have your box positioned so you can turn it off and on at the mains fairly easily as you may have to re-boot the box if the channel or guide gets stuck. You will no longer pick up stray channels on your TV (when we were on analogue we could tune the TV to get a couple of extra cable channels).
Good luck and have fun.
