I'm going to leave the finer details to those who fully understand them, but certainly the idea of overhauling the system is a fantastic and long awaited reform.
The year I took my GCSEs (2013), what I believe happened is that Michael Gove decided that the exams needed toughening up. This resulted in a new science syllabus being introduced, that had never been taught before, and certainly at my school, will never be taught again since the government phased out January modules. (I know this happened with science, but may well have done with other subjects, now pupils are taught linear science courses)
Of course what really happened is that exam boards changed the exams very slightly, but blew the grade boundaries totally out of proportion to be able to say to the government that they'd made them more difficult. This really affected my performance in earlier science modules.
My physics teacher showed me afterwards how the UMS boundaries had changed over the years, and there was a huge peak for the modules I was taking. I retook them in the summer and got 100 UMS marks in every science module I retook. Pretty telling don't you think?
Anyway, the point is, by just increasing the difficulty of the GCSEs, there will be a year when grades will drop, which won't be remembered in the future. Employers will look at the grades; they won't care which year they were achieved in, they will just think that those people didn't get very good grades compared to others.
By totally reforming the system, the changes will be instantly recognisable, and it allows totally new standards to be set by which we can fairly grade children's performances.
The other problem with GCSEs at the moment is that getting an A* isn't really that difficult. The A* should be reserved for the most intelligent, academic children who show a genuine interest in that subject. Otherwise, the A* is seriously devalued as an achievement. Hopefully gone will be the days when scores of people get 12+ A*s at GCSE.
There are huge problems with the GCSE system. To name one; the way in which pupils are made to sit an exam over and over again until they achieve an 'acceptable' grade; starting well before they are ready; is a brilliant way to destroy any enthusiasm they may have for the subject.
I do hope and believe that the new system will go a long way towards solving these problems.
There is, of course, the problem of the lower grades being much harder to achieve. However, I have a firm belief that the kinds of people achieving grades at the 'G' end of the scale should not be in school anyway, as it is clearly not the right place for them. In a lot of cases they would be far better off going into apprenticeships or other forms of vocational education where they could even be earning money.
All in all, I am really pleased that the GCSE system is being reformed.