The Commission had to report publicly within 5 years on how the new system worked.
Notwithstanding the stilted, self congratulatory tone, those documents are worth reading and contain a wealth of information that will delight antitrust mavens. It does seem that the system has worked pretty well and that national competition authorities have applied Articles 81 and 82 EC satisfactorily (sometimes more effectively than the Commission itself). Certainly, the rights of the companies investigated are more effectively protected on the domestic level than the EU one.
The report is inconclusive as to what changes should be made to Regulation 1/2003 to make the system better still.