Yes, a rather arrogant response from GSM. The EDI down to AGP has been late on more occasions than you mention and yes they are becoming a laughing stock - pax - and I have and deal with many on prof and social levels are using EZY from GLA and are going back to using BA via LGW .
Oh and incidentently, early arrival at AGP means very little to pax - while the airline might turn around a bot faster or even to schedule - pax are often left waiting in the arrival halls for baggage belt to become available at the scheduled arrival time.
Actually EZY were much worse than GSM in 2006 with 76% on time for GLA-AGP. GSM were 81.75% from GLA and 81.99% from EDI. For EDI (which is the only airport I have May stats) despite all the negative comments the GSM May on time performance is 73.2% for AGP, only marginally worse than 2006 EZY stats.
GSM definitely have capacity issues but methinks some doth complain too much.
By the way I have no affiliation with any airline or operator but hate hearsay.
Ex