If you are weighing up whether to take Additional Mathematics at O-Level, my answer is usually a straightforward yes. Here is why it matters more than most students realise.
First, it keeps your options open at JC and beyond. Most junior colleges expect a solid pass in A Math before they will let you read H2 Math, and H2 Further Mathematics is effectively out of reach without it. That matters because H2 Math, in turn, sits on the entry list for the courses students most often aspire to: medicine, the sciences, and engineering at NUS, NTU, and elsewhere. Skip A Math now and you may quietly close those doors years before you ever meant to.
Second, it makes ordinary O-Level Mathematics easier, not harder. A Math pushes you through tougher problems and a deeper toolkit, and almost all of that skill carries straight back into the E Math paper. Students who take both often find the elementary paper feels gentler by comparison.
So do not be put off by the subject's reputation. A Math sounds daunting, but you have two full years to grow into it, and with steady practice and the right guidance there is every reason to expect you will do well.