In the waiting room, the seniors will let you read through an example of the estimation questions first. Then you will be given 5 mins (i think?) to complete the actual question.
Do it in a step-by-step manner, make sure that it's easy for the interviewer to interpret. AND REMEMBER WHAT YOU WROTE, or just write bigger so you can see your answer from your end of the table when they are reviewing it. As long as it's logical, you will be fine. Never do the direct method e.g. I estimate 10000 transactions in a day, then i x2 to calculate the total for the weekend. Keep asking yourself why, why and why.
My question was about the number of Paypal transactions in a weekend. I used the the number of Paypal partners/merchants to start my calculation, and they interviewers asked why. So please be prepared.
The programming part was pretty okay for me. I only managed to complete unit 8.5 for the karel tutorial and was able to complete the test. Use if or while function as much as possible (try to simplify your code).
The rest of the interview was the usual stuff. No worries if you get lesser air time than the other interviewee/if the other interviewee got a more interesting life story than you.
And if IS is not your first choice, you will be questioned, so be prepared.
Oh and prepare a few good questions to ask for the FAQ. And that should be all. The IS interview was one of the easiest/laid-back interview I've been to, and I really enjoyed the whole 15 mins.
All the best!