Michael:
We have deployed to almost 7,000 users with no access code, which was a change from the previous PBX and Centrex service. It was well received by the general user community as it mimics the POTS service dial patterns they are familiar with.
During the decision making process for the removal of the access code it was also decided to implement a 7 digit internal dial plan. This also is standard in the users home area, so it was not a difficult change to train. The decision for 7 digit dialing was partly due to complexity of overcoming the pattern match in the previous 4 digit plan, and partly due to the multiple NNX codes we use internally (there are four). The ease-of-use was a given and the savings in administrative tasks beneficial.
To save on PSTN trunk usage we programmed translation patterns to remove the native NPA (if dialed) and look for a best match, then prefix it back on if the call needed to reach the PSTN after analysis.
Hope that helps out a little.
Tom