I'm somewhat puzzled as to why people think Wizzair's move is either bad or surprising. The purpose of an airport is to make it easy to move people and cargo between far apart locations. People and commerce are centred on Glasgow city centre and not a rural area. It's to the benefit of the masses if transport options are more convenient for them.
Ever since BAA lost its armlock on the central belt's aviation, it's been just a matter of time before competition started properly. The central belt has 4 commercial airports, it needs no more than 2. One (Dundee) has commercial passenger service only by clinging on with its fingernails. Another is scrabbling around to get by while aware it needs to spend serious cash on site repair.
Go to one of the main shopping streets in Glasgow on Saturday and ask Joe Bloggs which airport is easiest for him to use.