So this week's warning from MPs that students will start the diplomas next year with central aspects of the courses still under trial is worrying.
Teachers tend to complain that any exam reform is being rushed. It happened 20 years ago when GCSE was introduced, and it has happened at every change to the system ever since.
But the MPs' views are not the result of conversations with the profession.
They are backed by evidence from two exam boards which are concerned that the timescale for the introduction of the qualification is too tight.
Memories of the shambles that followed the last post-16 reform - Curriculum 2000 - are still fresh. Ministers accepted that the problems had arisen because the reforms had been rushed. Now they are in danger of making the same mistake again.
The Commons select committee is also right to question the complexity of a qualification that contains diplomas in 14 subjects at three levels of difficulty. It is vital that they are easily understood by students and parents. If they do not make sense to employers, they will be of little value.
Like the vast majority of teachers, the committee points out that the reforms would have been more coherent had the Government accepted Sir Mike Tomlinson's report, which proposed that A-levels and GCSEs should be subsumed inside an overarching diploma rather than running alongside them.
The difficulty of securing parity of esteem for the new qualifications, highlighted in last week's TES, would have been less acute.
The decision to abandon Tomlinson, taken just before the last election, made political sense but educational nonsense. Given that Tomlinson is no longer on the agenda, the need to make the diplomas work is pressing. As the committee chairman Barry Sheerman says, they are "an opportunity too precious to miss".