Funnily enough, I remember Shooting Stars never being the same when it moved to BBC Choice. Granted, they tweaked a lot of things and it may or may not have been because of the channel move, but it definitely changed and not for the better.
Shooting Stars didn't really move to BBC Choice, it was still on primetime BBC2 as usual (apart from that one they filmed on 9/11 where Ulrika didn't appear and it was so bad it was never shown on BBC2, just BBC Choice as a "special"). BBC Choice showed it first, but that's no different to when they were showing 24 first on BBC Choice. Hardly anyone had it at the time anyway.
A more obvious reason for the changes is because it was four and a half years after the previous series, and there are always going to be changes over the years. It's a bit like when QI moved to BBC1 and everyone said it had been "dumbed down" despite that fact a) when they recorded the first BBC1 series they still thought it was going to be on BBC2 and b) it was just the general increased informality you tend to get when a series has been running for a few years, when everyone relaxes a bit and gets a bit bored of the original format.
Besides, I would vehemently disagree with the idea Shooting Stars was any worse in that series, most of my favourite bits from Shooting Stars came from that run. I liked Vegas and Self as regulars more than Lamarr, they had great guests like Larry Hagman and brilliant sketches like Geordie Jumpers. And the Peanuts song.