I'd say 48 hours is plenty of time for visiting Dubai. I just ran the Dubai Marathon and spent four days there.

My take is that Dubai is a hugely important place in the world right now, but no amount of money can turn a tiny settlement and some date farms into a vibrant city with a distinct civic identity in the span of a few decades. What is Dubai now could have sprung up anywhere in the Middle East with sufficient money and political stability. Apparently without irony, Dubai created "Downtown Dubai" just a few years ago in what had been sandy, undeveloped land.

To be clear, I'm really glad I visited Dubai, and I would still recommend a visit to someone already planning to be in the region. But I say that in much the way I encourage those who want to understand the USA to visit Las Vegas. These aren't horrible places to visit, but before you go, make sure that what these places are fits with why you want to visit them.

BTW, only one must-see for me in Dubai: the Dubai Museum near the creek. Excellent small historical museum. I'd include the Burj Khalifa as a must-see, but you can't help but see it from anywhere in Dubai.