A repeated plot but a more serious tone has been added in DP. Some 'violence' has been added, the new villain for example doesn't seem to care to much what happens to Ash (main character) The art is sometimes very good (movies, special episodes etc.) but it can also really suck. It just depends what team does the episode (check bulbapedia) Sounds alright, good background music in japanese version. The characters are more developped and they're not all 'black and white' like they used to be. Nice anime to watch, not too serious but can be when needed to. Overall nice, no real action, the plot is spreadover 200+ episodes with mostly fillers. Art's not always the best but major episodes are mostly done nicely. Pokemon USA doesn't edit episodes any more so there isn't that much difference in dialogue and plot.

I personally watch mostly the more serious episodes but the fillers are more humourous. Give it a try, it's worth it.