I'm in my second year of Aeronautical Enginnering at Imperial now, I'll try to give you an overview of how are things here but if you have any specific questions feel free to ask!
First year is not too bad, there is plenty of time to have fun (whether that means getting drunk in clubs or getting involved in many societies :P ) and the workload isn't too bad. The deadlines are quite well distributed and the content of the course isn't that difficult to understand - first year is mostly for getting people to the same level. You will live in halls in your first year but which hall you get is a question of how much you are willing to spend and how lucky you are. Luck-wise it got worse last year as there is quite a chance you will end up in Acton but people who live there don't seem to be that unhappy.
Second year is where it gets worse. :P At times the workload is insane, especially in March when all the reports deadlines are piling up. The content gets harder and you are expected to do a lot of self-study. Having said that I think it's no different in Cambridge. The major difference is that at Imperial no one checks whether you've done your tutorial sheets and it's entirely up to you to do them (it has its pros and cons, currently I sorta regret not doing them 'on time' lol) although there are tutorial sessions when the lecturers will go through difficult parts; but then you will have to work quite a bit on your lab reports (which are not as important in Cambridge from what I've heard - someone from Cambridge can confirm?). You can try to get a place in halls by either being a hall senior or applying for non-first year halls (a new addition for next year) but living out is not that bad (both budget- and distance-wise) if you plan wisely and choose good flatmates.
The higher the year the more emphasis is placed on coursework and less on exams. You can find the details about grading, modules etc. in the student handbook on the departamental website, it's quite useful.
On the academic side you will get both excellent and terrible lecturers, sometimes the courses will not have a very good structure but from what I understand the department reviews them on a yearly basis based on feedback from students and they really do change things. You also get a personal tutor, with whom you meet weekly in 1st year and twice a term in 2nd year. They are your first point of contact in college related problems and are usually very nice.
They are supposed to do Maths tutorials with you every other week in Year 1 but since Maths wasn't too difficult for my tutorial group our tutor just showed us some interesting problems and told us about his research. There is also a senior tutor but didn't have much experience with talking to him. The teaching office will sometimes be helpful, sometimes not. :P
What Imperial does have a problem with is mental health support from what people say, mostly regarding stress resulting from the workload. I never felt the need to go through counselling but people complain a lot about the availability etc. I don't want to scare you off but sometimes you need to be a tough cookie to go through busy periods here (again, I guess it's the same in Cambridge) but it is manageable as long as you unwind from time to time and work smart.