had sky HD and Sky digital before installed.
both times, drilled a hole straight through wall (not sure if they checked if safe or not, but i presume so), ran cables straight through no sealant or anything.
Now as far as im aware when they drill the hole, there supposed to fit a plastic cover over the hole ?
the holes in the front living room, are ok, as they come in right next to where the tv is.
However we had it also installed in the bedroom (multiroom), and the tv is oin middle of room (plasma on the chimney breast, so that bit of wall sticks out leaving alcove type thing either side, instead of drilling in the corner where it would be out of view, the drilled the whole level with the chimney breast and the wire goes across the front of the alcove to the sky. (hope that makes sense), which is a bit of an eye sore.
so a mixed experience really, however on the plus side, they checked it all worked, was updated and the remote worked with the tv. on the flipside of it working after being told to wait 2 hours for the Hd channels to start to work, they didnt come on, so had to ring sky and get them to enable the sky hd channels lol
hope the above helps you decide