The syllabus hasn't really changed a great deal. The two main changes were an attempt to rationalise the content of each subject, so that material wasn't duplicated, and the inclusion of more up-to-date systems. The main rationalisation was between 022 Instruments and 061 General Nav where Inertial Nav systems, FMS and compasses were tested in both subjects. This means that, if you are learning from old books, very little of what you learn will be wasted, it just may be examined in a different subject. The additions have been things like FANS and CPDLC, but these are not heavily tested so your training provider should be able to bring you up to speed in those subjects on your revision course, provided it is done properly.
Bigger changes are the addition of new questions in nearly all subjects in the database, as ever these have not been properly validated and can cause problems by being outside the learning objective requirements, badly written, etc. As far as I know no question database provider has access to the complete set of new questions yet, although it is very tempting for them to say they do. The best you will get is feedback data from some of the exams.
Finally, some states have created their own problems as they realigned their databases to the new LOs by not setting up the algorithms for exam creation properly. In the UK there have been problems with General Nav, which has more questions in the new syllabus, and with 032 Performance where far too many graph questions were included for some months. Both these papers made students very short of time. General Nav now seems to be sorted, Performance does not.
These are the pass rates for old and new papers in the UK for the last four months, apart from Performance they look OK to me, but draw your own conclusions:
