The key success factors in using 4GL tools seem to revolve around the words "commitment" and "attitude".
Unless all members of the team are committed to the new technologies, and the methods they use, the result will almost invariably fail to meet expectations.
Additionally, they must have a positive attitude. This problem is most commonly found among long time 3GL programmers, who are not really interested in, or committed to, new 4GL technologies.
These two factors are probably the most critical in the success or failure of any application development and should never be under estimated.