In stark contrast to the Open Society Institute, ECI seems to think the election went reasonably well. From the ECI statement:
The Congolese people went to the polls yesterday to elect a new president and a new parliament. Early indications are that the turnout was generally high with polling booths remaining open long after the official closing time of 5 pm. Eastern Congo Initiative (ECI) witnessed a high level of participation in the voting and celebrates along with the Congolese electorate as they nobly exercise their mandate to democratically elect their leaders at the local and national levels. We also recognize that in spite of great odds, voting day was largely peaceful in the East of the country.
The elections should be considered an achievement given the vast size of Congo, and the almost insurmountable constraints of terrain and climate. In many of Congo's remotest corners, people were able to vote on time with the necessary resources. The National Independent Electoral Commission (CENI) has achieved a striking feat, implementing a nationally organized election with limited support from the international community.