Hi,
We have the Bugaboo bee plus and am very happy with it - been on a number of buses and tubes with it and it is very easy to use, fold and very lightweight.
It seems that whatever buggy you buy, everyone seems to buy a McLaren or a similar umbrella-style pushchair which is easier to travel with when the kids are a bit older, however these puschairs are not good for newborn babies so I guess you would still need to buy another good puschair (like the Bugaboo), or like someone else mentioned get a good baby carrier cause newborns love that!
Good luck,