Yes, 1.4 seems harder than anything I studied for in 1.2.
I studied for the 1.2 exam quite extensively, between programming contracts, then jumped into the 1.4 exam and passed, but not to my full satisfaction.
The difference between mock questions for the 1.2 and the questions I found in 1.4 was significant - there were still standard bread and butter questions, but there were also mind bending questions relating to class interaction, etc., that I had not anticipated.
O, I also knew inner classes backwards too.
So my advice is to go over the fundamentals very well - rote learn, as it stands you in good stead in the workplace when you need to be fast about problem solving. Then, spend another good while thinking of example questions that have to do with one, two, or three classes interacting and presenting a problem - about threads, casting, method overriding, etc..
Nick