I applied for the Extreme Blue summer program they run every year, and although it was probably the one internship I really was excited about, I ended up having to turn them down before the last assessment round because of another offer.
I'm quite puzzled as to why they have a first round assessment day in mid-January, and then wait until end-March/early-April to have the second round assessment day. To me that's like saying they don't want the top candidates for it. Any student worth his salt would have applied to a range of companies, and many would have come back with offers before end-March, thus posing the dilemma of rejecting and placing all hopes on IBM, or playing it safe.
Plus they have a really wierd recruitment methodology. During my assessment centre, everyone applying for the technical side was doing some sort of computing-related degree, and I'm doing Biomedical Engineering. I felt so out of place and hopeless, but it turned out that I was one of the few ones that passed through that round. I've not had any notable achievements in programming, so I'm really curious as to what IBM is looking for...