When you first switch over to the new system the operators will be slower at first. As they become familiar with the new system they will gradually return to the same, or even a higher, speed. This learning curve effect can take a few days to a couple of months. You can expect initial resistance to the new system if the old system was satisfactory. Some people adapt more quickly than others do.
Psychological factors have a lot to do with the learning curve.
If operators approach the new system with a positive attitude, things will progress faster and smoother. It is important to prepare them for the change and show them how the new system is going to be better. Involve them in the process and solicit their opinions on how to improve jobs. Someone on your staff should learn to set up new data entry jobs and make modifications to existing jobs in the future. It is not good to be at the mercy of a vendor or outside consultant for every little change that you need.