I visited for the first time on Thursday and my thoughts at the time were identical to those of Smirnoff's. I didn't go for the pre-flight dining but had a look at the menu and it was certainly not a restaurant which I'd pay to go and eat in in London.

To add to what Swanhunter wrote, I remember reading a post from someone on here who said that the service in the Concorde Room is a shadow of its former self, e.g. in the past, where the staff knew the regulars and would (for example) go out into the terminal to buy a particular drink/magazine/newspaper if that was unavailable in the lounge.