Sydney - AWESOME city, I love it. Its just a very cool place, sunny 300 days a year, nice people, very cosmopolitan, lots to do, great airport.
Paris - Lots of great places to eat, not as exciting as Sydney, but a little more sophisticated
Zurich - Great airport, nothing overly exciting in the city, good chances to go skiing in the alps in winter though
Amsterdam - nice city, great airport, Red light district, lots of bars and clubs. Cool place
Madrid - Don't know much about the place, not so good airport, not very interesting city AFAIK
Singapore - VERY nice place, but VERY VERY VERY expensive to live in, an average family size saloon is gonna cost you about $160,000 a year. Most people live in over priced small apartments. Very clean though, but more for shopping than anything else. Nice airport too!
Bangkok - Uhhh.. Its got a nice culture, a very nice market where you can have nice food for very little money. Some sides of the city aren't so nice (the royal orchid sheraton, where I stayed wasn't in the nicest part of town), not too sure of the economy and alot of unfinished hotels. Lets hope the airport is better than the current one
Hong Kong - Heard its a nice place, cool airport once again, very cosmopolitan, apparently still has some orient/chinese culture left (unlike Singapore).
Tokyo - This place is f*ck off huge. I think there is a specially-designed city just outside tokyo thats alot nicer.
Moscow - I've heard it can be a nice place, cool climate (freezing in the winter, hot in the summer). Nice people, crap cars, cool airport (if a bit crappy).
Dubai - very very hot!! Its quite an odd place, alot of very rich people living there.
Doha - I don't know much about Doha at all, except where it is.
Almaty (strange sounding, I know) - ......
Prague - I've heard its a nice place, very nice people, not as you'd expect a big city, quite picturesque.
Warsaw - I don't know much about Warsaw.
Vienna - Ask Peter Unmuth