For me.. the PT hit on the relationship between Obi-Wan and Anakin. Something just hinted at in the OT, but PT I thought really hit home.
Was hoping to get see more of that relationship and how they would wind up answering the OT's ANH dialogue.
Luke: How did my father die?
Obi-Wan: A young Jedi named Darth Vader, who was a pupil of mine until he turned to evil, helped the Empire hunt down and destroy the Jedi knights. He betrayed and murdered your father. Now the Jedi are all but extinct. Vader was seduced by the dark side of the Force.
and of course, how it translated to ESB's Vader Revelation.
I thought the PT did a good job on showing the mentoring/comradery between Obi and Anakin.. with the humor quips added as icing on the cake. Always enjoyed the scenes when Obi/Ani exchanged dialogue, and thought it illustrated the deep bond they shared and the tragic consequences of the betrayal afterwards, due to the Council constantly denying Anakin and the Emperor's coercion of those decisions to lure (the naive) Anakin to his side.
In an afterthought, and I'll probably catch hell for it
but I thought the PT did such a good job with it, that when they were re-united in ANH.. it was a little dis-servicing to the relationship (hindsight though is a double edged sword). The scene seems a little more dry after the events we saw in the PT.
The re-uniting (ANH) is one of the few scenes I thought could actually be improved upon given what we know now about their relationship (now). Probably one of the few changes I'd actually have welcomed had Lucas decided to "special addition" that portion. Though without Alec Guinness (RIP
) that too would be dbag move to add/alter now.
oh! and of course, R2D2 is much more of a badass