The Good Practice Guidelines for GP electronic patient records, issued by the Department of Health, Royal College of General Practitioners and the BMA, makes several positive references to PRIMIS:

The largest repository of evidence for inter-practice variability in recording quality in GP computer records is PRIMIS.

The Guidelines go on to say:

PRIMIS and GPRD [The General Practice Research Database] have been instrumental in defining standards and procedures for improving data quality in Primary Care in the UK.

You can Download The Good Practice Guidelines.