We have been operating the Private Portal for a number of years with many thousands of participants. It is a tested and proven tool! Occasionally we have an access problem often because the members have changed user names or forgotten passwords etc. but basically it works without drama. You will find the Private portal is very popular with your members simply because they find access to everything so convenient. If you monitor the Portal Activity Tool over time you will notice that many members go back on multiple occasions to access and/or view results of surveys. They often refer back to surveys they participated in years ago.
Believe me your once your members get the hang of it they will use the Private Portal regularly all hours of the day. It is viewed as being a very valuable tool offered by your organization. Don’t forget it will be branded with your logo so every time they visit the portal in the middle of the night (which is common) to review their results they see your brand!