I had Ondigital for a while
Actually the free to air digital terrestrial channels were of excellent quality, from what I saw better than digital satellite. Pay channels were pretty variable.
There was a difference in receiver quality as well at the time.
I ended up on a £3 per month deal for a year, then a bit more until they went bump.
Anyway it started for me with a Sony IDTV one of the first, outstanding picture quality, but lots of unusable channels - until the CAM offer came out, no CAM so they lent me a Nokia Mediamaster box with lop sided remote control, definately a step down from the Sony TV, anyway connected it to a Sanyo Beta VCR I could record digital TV. However we ended up watching 2 channels a lot and the others a bit. Discovery Wings and Carlton Food Network.
Eventually the OnCAM arrived and a man from South Wales updated the TV to handle it. Now I got into the recording issue, swapping cards was painfull CAM in back of TV.
All through this period there was lots of information about hacking the cards - I will admit I wanted to but not for piracy issues, I wanted one for TV and one for Ondodgy box.
Anyway there were a lot of people getting Ondigital for free, but many many more who opened up their basic subscription to a full subscription, this possibly hurt more than they expected, people rather than buy a sport subscription had the basic one and opened their genuine cards to a full one. It was all over the digital TV groups and links were everywhere.
Near going bump time Ondigital wanted their box back but collapsed just before they sent for it. It didn't last long before failing and I ended up getting a Pace Twin.
Ondigital was a good go but was badly run, good channels dropped (so I cancelled - literally within days of shut down).