I own the 14-24 2.8 and the 16-35 f/4, and I just bought a Nikkor DX 10-24 f/3.5-4.5 for my new D3200. The 10-24 is a super sharp lens. It may just be the 24 mp on the D3200, but I think that it gives my 14-24 a pretty good run for the money considering that it's half the price.
An f/3.5-4.5 lens is not that slow when compared to a 2.8 lens. It's only 2/3 of a stop slower at the wide end and 1-1/3 at the other. Now if we were talking about f/1.4 primes that would be a different story.
Here are a few samples that I posted in the D3200 forum. The one with the 400% crop of the serial number was not focused on that serial number.