If Puerto Madero is exactly what you want, and you've got the money, then don't let what anyone says stop you from living there.
That said, what the other posters have indicated about it is accurate. While it is most definitely safe and fancy, it feels like a very isolated Green Zone that has no visible relationship to the rest of BA whatsoever, which just makes one want to ask: if you're going to move all the way to BA, why go there? From where I'm sitting, I can have that exact lifestyle here in a part of Atlanta called Buckhead, minus the water front. Puerto Madero is an imitation of something [expensively] available in many, many other parts of the world.
As others have pointed out, it greatly decreases your ability to leverage one of the best things about BA - its very comprehensive, if imperfect public transit system.
Also, it's not very lively. Although there are some places to go there, it feels kind of contentless, eerily quiet, almost like the deafening roar of silence you feel when you walk into a museum gallery or a funeral home. Personally, I don't think that's what most people that come to Argentina are seeking; aesthetics with that kind of temperament are signature hallmarks of rigid Anglo-American and Teutonic civilisation. However, if it's what you're seeking, by all means, go for it.