Own personal take on this:
The Specials are a good band, they've been around for years, lots of people may know the name or have heard a track by them and perhaps not known it was them. They have legendary status to some folks and not so much others. However I do find it odd that they would close somewhere like IR without a big supporting line up.
As for U2 - Legendary band, have consistently delivered for years, though likely wouldn't play to less than 60,000 now, amazing live but it still doesn't hide the fact the Bono is a bit of a twat and The Edge has a tendency to use that delay effect a little too often.