I recently applied to a selection of Top MBA programs: Harvard Business School, Kellogg School of Management, Columbia Business School, IMD and INSEAD.
The PDF-based application system proposed by Etheryl for INSEAD is the most convenient for the applicant:
-I was able to work on my application offline
-considering the effort needed to submit a good application and the restricted amount of time at my disposal, I was glad to have the application file handy at anytime, from an "enhanced" editable PDF.
-The ability to submit an electronic signature is also a plus as it ensures a stronger level of security for both the University and the applicant
-The added flexibility for the recommenders: they can access, edit, save and submit their recommendations online.
-The online application status for the applicant is convenient as well as the ability to attach -and modify- a picture to the file.

As an applicant to INSEAD, I was extremely pleased by the overall application experience and the sophistication of the electronic tools.