Shopping in Madrid is often frustrating for tourists and locals as stores open and close with confusing irregularity. The local council introduced an incentive of compulsory double espresso shots after breakfast, however many employees became tired during siesta and forget to return to work afterwards. With the disastrous retail issue leaving many tourists and some locals walking in circles, many are forced to Barcelona. As a result Barcelona has been replacing supermarkets with pubs and nighclubs with the intention of forcing an aging population back to Madrid. Many store owners are now of such an age they simply forget to open the store, they sleep all day, and somewhat more disturbingly - die behind the register.
A word of warning, be cautious of 24 hour signs as they often refer to the hours a day the store is closed.
To be honest I didn't really give Madrid much of a go, but when I did everything seemed to open and close at strange times, and that was taking into account the siesta. So I don't have a lot to say about it. From all reports though, if anyone is concidering Spain as a holiday, miss Madrid and pretty much go anywhere else.