Sorry I've only just seen this (not been on TSR for a while with being very busy)! I've not been in Cambridge long (had a week and a half of lectures, 2 materials practicals, 1 chemistry practical and a physics supervision), just about long enough to settle in, so these are just my first impressions. I'm loving being in Cambridge, the course, the people (though an overwhelming number of new people to meet at first!), and there being so much to choose between to do in terms of societies, music etc.
Apart from I've now caught freshers' flu haha.
How you find the natsci course might depend considerably on what options you choose, I'm doing physics, chemistry, materials and maths B (pretty typical for chemeng). So far the lecture content hasn't really covered anything I've not done before, which I suppose it better than me not understanding a word of what's said in them, apart from of course materials which is completely new to nearly everyone doing it, but I'm finding the materials course more interesting than I expected, and the materials practicals especially are a lot of fun. Apparently it does get harder though! (Other students keep talking about the work they've got to do and I don't really feel like I've had much yet!)
The lectures vary from lecturer to lecturer. For the first part of the chemistry course, we have Dr Wothers, who is an amazing lecturer (have you read "Why chemical reactions happen?", the physics lecturer brings wind-up plastic toys to amuse us mid-lecture, the materials lecturer gives out chocolates for audience participation!
My grades and UMS are all on my profile.
As for the interview, I was recovering from a head injury at the time so I don't remember it overly well... I don't know the format of the interview at Churchill, but at Trinity for natsci we had a 1 hour pre-interview test, and then the interview was spent almost entirely going through the bits of the test that weren't completely correct!
Best of luck with your application!!
Let me know if you want me to expand on anything!