If you didn't like Uru this expansion won't change your mind.
TPotS is set whenever you decide to do it. For most players it is after the original Uru game, and To D'ni (which is mostly just exploring the underground city of D'ni, anyway). In TpotS you're not really given a clear objective like you were in Uru. Ultimately you need to learn how to navigate the "Path of the Shell", so you visit two fairly large ages where you'll find scattered notes and puzzles that will help you in this regard.
The puzzles in TpotS are rather tedious. Two of them force you to sit there and twiddle your thumbs for fifteen minutes. Sure, good things come to those who wait, but people play games for entertainment. And there is nothing entertaining about standing in one spot for fifteen minutes.
The graphics and audio are for the most part the same as they were in Uru. There is some new music for the To D'ni and TpotS areas, but it sounds so similar to what was in Uru that you won't really notice much of a difference.
The Path of the Shell is poor as far as expansions are concerned. It adds several new Relto pages, and some new clothes items, but the most important content is the story it adds which is practically non-existent. I can't recommend TPotS to anyone, honestly, and if you didn't like the original Uru than this won't change your mind.