Hi Bharani
Thanks for your input. Parallel download is certainly useful. But this still leaves me with 1 file per customer_id which I have to join together since I don't wanna deal with dozens or hundreds of files.
Other platforms (e.g. DoubleClick) have the functionality to run reports for several accounts in one report out-of-the-box and it would certainly come in handy for many of us if AdWords would provide this functionality as well.
Anyway, I'll try to use the parallel download for my implementation.
Reagards Marcel