OP, the simple answer I suspect is that it depends a lot on the student. There is no doubt that Imperial can offer a world class education, and you should not be put off by the poor experience Borojo's daughters seem to have had. Other's will have had a great time.
DS is not at Imperial, but in his third year at LSE. Several of his friends went to Imperial as did a large group of DDs friends. My, slightly random, observations are therefore slightly second hand and based on experience of a similar international and specialist London University, one which I also went to.
DS's choice was influenced partly by the fact that he was not offered places at Warwick, UCL and Cambridge. I think, for the reasons Goodbye gives up thread, he would have chosen Cambridge and I would have urged him to take another look at Warwick and the different student experience it offered. However I don't think he regrets LSE at all and indeed is only applying to there and Oxford for his Masters. Academically he feels departments elsewhere are less interesting.
Anyway:
- Academics. If you are really really interested in your subject and this is your main driver in choosing where to study, the specialist London Universities should be near the top of any list. Ability to engage is important, and this is where London may differ from Oxbridge. These institutions will all employ interesting academics whether at the start of, or established in their careers. There is lots of scope in London, via societies, voluntary lecture series, public talks, office hours, volunteering to help post-grads with research and more, to engage in your subject beyond lectures and classes. Academics normally are very happy to support students who share their passion for a subject. Yet DS has been surprised at how few take advantage of office hours, and indeed that he is the only UG who seems to have asked if he could attend a really interesting seminar series. A close friend of his has had a similar experience at Imperial, where he has picked up amazing international opportunities via engagement in a specialist subject society.
- Flexibility. DS has had a wide choice in options, and has been able to tailor his degree to reflect his emerging interests and apparent talents. (For some reason he is doing better at maths than he did at school, for others it has been the reverse, but scope for both groups to steer to and from technical elements.) Friends of his who received rejections from Cambridge, saw the ability to specialise at Imperial, rather than spend a year studying NatSci, as a real silver lining.
- Overseas students. Well firstly "the Chinese" are a diverse group. Half will probably be from the Chinese diaspora, rather than mainland China. DS' Chinese friends come from Wales, Harrow, a British Public School, and the International School system as well as Hong Kong. One of his flat mates was from mainland China, but happy to mix. From what I have heard, some will work very very hard, others, once away from family pressure, not at all. DS has picked up some of the culture of hard work (and how to make dumplings), which can only be a good thing. And Imperial really is not just Chinese. It is amazingly diverse, so one boy we know has friends from Iceland, Portugal, Malaysia and just about everywhere else. For many Europeans, Imperial is just as big a name as Oxbridge, and living in London is part of the attraction.
- Social life. It depends what you want. DS was very happy to avoid a full blown freshers week, and be in a culture which does not require regular drinking. London has lots of layers, so students find their own city, whether it is art house cinemas showing Manga, North London pubs screening live computer gaming in Korea (I know!), seven a side football leagues, off-peak times in climbing centres, LSE's Saucy disco, and so on. There are lots of joint events/competitions involving student societies from the different London Universities. One advantage of London is that student life tends to be based on University rather than hall, so accessible to second and third years and Post graduates, as well as first years. This is not true at some campus Universities, Warwick is an example, where late night transport from campus can be tricky. Athletics Unions in some London Universities have a real reputation for laddish behaviour, wild nights out and for conducting team trials in the bar, thereby catering for the party animals. Imperial has very good sports facilities. (I am not sure about geologists but going back many years, I still remember some very good parties at the School of Mines.)
- Living. London is expensive. However Imperial is reputed to be the best off London University which has led to it having one of the highest student satisfaction rates in London. (And London Universities seem keen to maximise their student satisfaction rates because of the impact on league tables.) Imperial, like others, has ways of supporting less well off students. Imperial has relatively good accommodation provision, some of it linked with its recent expansion at Shepherds Bush. A London based friend of DDs has a bursary which allow him to spend his first year in hall. LSE too is keen to find ways for good students from outside the South East to attend. I don't get why Borojo's daughters would choose to live in the Elephant and Castle, which is expensive because of its transport links to the City. Something like an ex-Council flat, using the living room as a bedroom, near Clapham Junction (a quick train ride to Kensington and buses to everywhere else) would seem more sensible. Again though it is worth remembering that wherever you are, you are probably better off than the second year Warwick student in the bus queue in Leamington Spa worried they will miss their 9.00am lecture. (In contrast a London student will be able to study in the library 24 hours a day so will be less worried about slightly cramped accommodation.) Not spending on drinking and clubbing, and eating cheaply in China Town or cooking with friends means that once his rent is paid he seems to spend less that many other MN DC.
However, living in London is a challenge, and if your primary aim is a "University experience" rather than your subject, and if self study skills are not fully in place and you will want support and encouragement to engage, there will be better places than Imperial. That said Imperial seems to work for younger students, at least those who are able to commute (DD knew a couple of 14 year olds and a 16 year old who went there, presumably treating it a bit like a sixth form college) and for British ethnic minorities who seem to enjoy the diversity and the lack of an all-pervading drinking culture. For a good student it will deliver a very good education and great job opportunities. Students in London emerge very job ready.
One concern, in case anyone from Imperial reads MN, expressed by DDs friends both at UCL and Imperial is a tendency for Mandarin speaking graduate teachers to respond to questions posed in Mandarin in their native language. It leaves other students feeling that they have received less complete teaching than their peers. And indeed irritates a Mandarin speaking friend of DDs who says he wants to learn his engineering in English. If he wanted to learn in Mandarin he could have stayed at home.