I've been re-watching the entire series recently and can only (largely) echo what others have said: the specials are easily up there as some of the best in the show's history. Although, having said that, I definitely prefer the earlier 30 minute pure-sitcom episodes in general.
On laughter tracks, I found it really, really jarring and off-putting to have To Hull And Back so cold and clinical. It's a very funny episode no doubt, but it needs that extra sparkle and warmth, both of video (rather than film) and the laughter. I think they realised this though, as all the others I've got through (not yet finished the marathon) do seem to have an audience.
A Royal Flush really, only get for completeness. It's ... I can't even describe how awful it is. Perhaps if the DVD release didn't have almost 20 minutes cut out it'd be better, but the hour is about all I can cope with.
In summary: get it all.