As cities go, its pretty good. Great place to visit and spend a few days - also a great place to be a student.
To live though? no chance, unless your rich its a huge waste of money, and for me personally it lacks a huge amount of the things that I want out of a place to call home.
No easy access to beaches/the sea, no great wildlife/countryside, no outdoor activities etc. But these are not criticisms of London specifically, but most large cities.