We went through this dilemma recently too. We are in SA (cut off April 30). DS's birthday is 23rd April so he will be 4yrs9m when he starts.

We changed our mind a million times, but in the end decided to start him in 2014 instead of 2015. He is ready now quite frankly. He used to be quite shy, is now very outgoing and loves the the schoolroom type environment in the childcare kindy room - can spell and write heaps of basic words already, knows his full alphabet, left, right, and his vocabulary at 4.5 is very developed. He only goes to CC twice a week but we consulted with his care givers on their thoughts (one is a Junior Primary Teacher) and they thought he was ready too. We have chosen a private school so the classes are smaller etc and are really comfortable with him starting in 2014. I'm sure I'll think he's too little on his first day though!

Every kid is different - I think you need to make a judgement call on your kid, rather than a generalised opinion, my first thoughts were wait a year - I've now realised that holding DS back would actually be to his detriment, he is ready.