There are alot of people here who are commenting, even though they know nothing of political study. They simply refer to rankings and perceived reputations. Let me defend what i said for a minute.
Firstly, granted i was a little harsh to say Notts was a lot better than Sheffield, but i was not wrong to say Sheffield is slipping, and i shall explain why. Politics tends to have fads where some fields (and there are lot of them) are popular. Sheffield has been incredibly strong because they used focus alot on European politics, with two of the main academics (Colin Hay and Ian Bache) there. This put them at the fore during the nineties when Euro studies were all the rage. However, nowadays IR and security studies, as well as political history are currently the most popular. This is where Sheffield is let down. They are not doing the popualar stuff at the moment.
All i am saying is that at Notts academics like Stephan Wolff, Wyn Rees, Richard Aldrich (who's just left), Steven Fielding, Neville Wylie, and Rod Thornton are publishing loads of stuff in the main journals on popular stuff- not to mention Phil Cowley, Andreas Biesler and other top academics there. They have also just introduced a new AAA offer MSci IR undergrad degree (the only one in the country) which has created a buzz in the field and attracting lots of applicants.
The IR field is the place to be at the moment, just like it was Pol Sci a few years ago, therefore LSE is the best (with Buzan, Cox and Brown), as well as Aberwystwyth and St Andrews. Kings has a weird reputation because it only does War Studies, and although it is immense at that, it is a small field of IR. Cambridge is not even very good for IR, even though most would just assume it is.
Sheffield, has a great all round quality - the RAE proved that, but it is just that its main academics are not doing the important stuff at the moment, with the RAE does not reflect, and this is why in my view it is slipping.
If you talk to actual academics they will tell you the departments which are doing all the important research at the moment and the ones with a buzz - and Nottingham would be one of them, along with the ones i mentioned above, as well as Warwick.
Anyways i dont need to defend Notts, i dont go there anymore and im doing an IR postgrad at the top place in Europe, all im saying is that i have my ear to the ground a little bit when it comes to what academics are saying.