The main complaints from what I've seen on that mailbase are as follows:

1. Having to buy a stock of cards from the NUS and therefore incurring a finincial risk.

2. The issue of a national database that may be created.

These concerns are mitigated by the fact that:

1. What seems to be the preferred option is a high-spec online administration system where there is no risk on the part of the Union.

2. There will be no national database - Unions must retain their own data, this is paramount. Whilst this is a big issue, the strength of opinion is against a national database.