[Warning: Long post]
Graduated from Manc recently. I was a student rep coordinator for my programme so ended up attending many meetings with students and academics. So I can say a lot about this from both the student and university perspectives.
The big problem with Manchester is its size, with over 40,000 students it is very difficult to give personalised service to all. It used to be that you only got personalised experience if you asked for it, and we know most students are not proactive, this led to poor student satisfaction. Now things are changing and should be reflected soon in the ratings. For one, in my last year it was made compulsory for students to get personalised feedback on their coursework within 15 working days. More office hours were allocated by lecturers and the university (at least my department) stepped up its training for tutors. I confirmed this from my friends now doing PHDs and tutor.
Manchester also had a VC who after the merger focused more on research and international reputation than teaching quality. Promotions were tied research which meant lecturers were more concerned about getting published and attending conferences than dealing with student issues. This is also changing as the new VC has refocused the university on providing excellent teaching and a great student experience. To show how serious they are, a student experience directorate was formed last year and a new registrar was brought in from Loughbrough (known for one of the best student experiences in the country)
UK rankings put more weighting on student satisfaction ratings while international rankings emphasise research, awards and reputation. The former works against Manchester because of the reasons above and the latter helps Manchester as depending on how you read it, Research Assessment Exercise (RAE) puts Manchester as a top3/top5 research institution int the country. Manchester also has the most active number of Nobel laureates in the country among its staff, even higher than Oxbridge.
For employment, outside of the 'triangle' Manchester is the most heavily recruited university and its career service has consistently won best career service awards. From a branding perspective, Manchester is seen even more favourably internationally.
Overall, I think Manchester is a fantastic university that will only get better. Enjoy your time in Manchester, I certainly did.