From what I've heard, Dr Goh Siak Ming has a really good reputation at KKH, a friend of mine delivered under him and said he was very calm and reassuring throughout, especially during the actual delivery when things can get quite nerve-wracking. People who've been with him generally describe him as experienced and steady, which counts for a lot when you're in labour. If you're considering switching, he does seem to be a well-regarded choice, so it might be worth going for a consultation first to see if his style suits you before committing fully.