I think the trade tends to prefer (and thus promote) set-top boxes over IDTVs because it's a lot less hassle for them in the event of a return, due to the difference in physical size. There are still plenty of places in the UK without good digital reception so returned sets have been a bit of an issue for them.
Having spoken to various users, retailers, installers and manufacturers I can honestly say that most of the people who say negative things about IDTVs don't actually know what they're talking about. One particular sales manager in a well known high street retailer even told me "There's no such thing as a digital TV, it's just a normal TV that they've stuck a set-top box in the back of. That's why I always recommend Sky to our customers."