The music used is consistent cover versions from start to finish, perfect for a Saturday night audience who have proved that they have no real demands what with watching Stars in Their Eyes for the past 15 years and all. The contestants belted it all out with a lot of effort and then the judges praise them or criticise them while the audience (home and studio) boo and cheer as if they are at a pantomime. It is a fantastically cynical show that was originally criticised for coldly manufacturing an act but quickly moved to manufacturing everything about the show. The various bland acts will turn many musical fans off simply because it discourages originality in favour of the hits and the gloss of the pop charts something that will please many viewers but personally I prefer music that I find interesting more than just soothing and familiar (in fact I am trying out Jean Grae for the first time while writing this). With so little between them it comes down to personality something that the acts have safely tried to turn down to safe levels apart from a few guys that try to be "themselves" before being voted out. This leaves the judges to try and push forward their personalities and provide drama and the pantomime material, something that they easily do.
The delivery of Ant & Dec helped the proceedings because it did help keep things light and help the judges and the audience realise that it was all a bit of fun and not to take it too seriously. Contrast that style with the "the whole world hangs on this moment" delivery of X Factor's Kate Thornton and you'll see why it helped the series. The judges were a bit more relaxed and balanced as well, although Cowell was already starting to turn into a parody of himself long before the first series even finished. The acts that the show produced have mostly all died away Rik Waller dropped out despite making it through to the final rounds (giving some rubbish excuse that suggested he was offered a nice deal if he just got his fat self off the show as the producers got rumours of efforts to comically let him win) while similar biggy Michelle McManus has taken to letting the world see her diet to keep things moving. Credit to Will Young who has managed to keep it going despite being so posh that the Royals think he is a snob.
Overall, like Pop Stars, a cynical product that gives the public the illusion that they are in control, letting them pay to create a pop star and then asking them to pay again to buy that artists' cover version singles. It works because the formula seems to have won over a large section of the Saturday night television crowd but personally I find it drearily staged and lacking in anything of interest as the TV blares cover version on the months long march towards yet another big selling first single followed by a gradual fade away.