I seem to be of the opposite opinion of a lot of people. I think the 2 piece TNG uniform is a decent looking uniform (that being said, the FC uniform is my favorite TNG-era uniform).
Probably the one thing that bothered me was the heartbeat stripe in the midsection. It looks too 1980s to me. It would have looked better to be straight across the midsection instead.
Now, I liked the color scheme of the DS9\VOY uniforms, but, I did not like how they looked more like a jumpsuit than a uniform. The FC uniforms fix that look. Personally, BESIDES just using the FC uniform from the beginning, if I were to design a uniform based on the TNG series uniform, I would have combined the the 2-peice TNG style with the DS9\VOY uniforms: making the uniform all black using their shoulder color scheme of the DS9\VOY uniforms.
The TNG uniform I had a problem with and a special hatred for, though, was the dress uniform that was literally a dress!!
Worf/Riker from Liaisons:
WORF: I do not see why it is necessary to wear these ridiculous uniforms.
WORF: They look like dresses.
RIKER: That is an incredibly outmoded and sexist attitude. I'm surprised at you. Besides, you look good in a dress.
This to me was not a practical dress uniform and took 'dress' too literally.
The dress whites from the First Contact era did a better job of looking formal without looking completely out of place. I do wonder, thought, if there were a simple evening dress/dinner dress uniform more formal than the service uniform, but less formal than the whites.