I thought of going up, but couldnt see spending the 125/200AED to go half way up the building. (For me), the major architectural thing to see is the Khalifa. (And Burj Al Arab) along with the Palms ofcourse. But you'll be in the Khalifa, you can see the Arab, but it'll be real tiny, and I dont think you can see the palms.
I was also concerned about the fog/haze so I didn't bother.

However, I do understand why people want to go up. If you are worried about weather, you can always show up when its clear and buy a ticket on the spot. Its just an (even more) outrageous 500AED (I think).