Lots of people like London. I'm not one of them, but then I don't like big cities. I would say my biggest gripe about London is the frequent transit failures. I literally can't remember the last time we didn't have someone come in an hour late because of some train/bus problems. My second biggest gripe is the frequent transit strikes ;-). If it's not busted, it's not running because management and workers are fighting with each other.

Especially if you are comparing London from 20 years ago, I would have to say that it is much nicer than it used to be. I lived in London 2 years ago and also 20 years ago. I remember 20 years ago coming home and literally being able to draw pictures on my arm with the grime that accumulated during the day. Blowing my nose always resulted in black snot coming out. The Thames was filled with garbage. Those days are mostly gone now. Hell, tours on the Thames is considered a fancy thing to do these days.

The things I think are not quite as nice (and I'll brace myself for the backlash)... Culturally the city is kind of confused IMHO. 20 years ago it was vaguely European, but really English when it came down to it. You could still get a decent Sunday roast in any pub in London at the time. Now it is decidedly multi-cultural. I think young people will definitely prefer the London of today, and I won't blame them, but personally I miss the London of times gone by. These days you have to go further afield to get more of an English cultural experience, IMHO. Not necessarily a bad thing, but like I said, there will be people who prefer one over the other.