How are your grades like? Mine is UAS 81.25, H1 Math A, O Levels were pretty decent, and I've got called up for an interview on 30th April. I asked the lady and she said it's because I'm a borderline case (I guess small cohort, so cut-off can rise a lot in a yr). I have a friend from poly, and on his side everyone he knows who has applied for IS has been called up for an interview.
Basically, if you scored about the same as me, you'll be getting your call at least, and if you scored much better (Math inclusive)... Wait for acceptance!

There's a guy with UAS 85 who received direct admission.
I've not received the reporting email yet, but there's a Personal Statement of less than 500 words to be submitted, and also candidates should bring a calculator for a 30 min Problem Solving/Logic test. That's all I know for now, will add more details later.