They are extremely slow. But the problem is not only CIMA, it is "Aviacion Civil" (Spanish CAA) as it's them who decide whether you are fit or unfit.
CIMA is the only place in Madrid, however, you can choose some other places in Barcelona, Seville and Valencia. I heard they are better than CIMA and should be able to tell you if everything seems fine, but you can still expect the 40 day waiting time to certificate issue.