I love both the anime and the manga, and currently I'm on my second way through the anime.
The first 40ish episodes of the anime are alot more fast paced then what it is now. That however is logical because I think the Anime started 2 years after the manga?
To me the anime and the manga are equal. The anime succeeds in some areas where the manga fails and vice versa. For instance some comedy scenes are more funny animated, (I thought Bon Kurei was way funnier in the anime) but in some parts its a swing and a miss. Eg. When Luffy says to Paulie, don't get mad at Lucci, its the pigeon! cracked me up in the manga. Not so much in the anime, and I watched tht part first before I read it.
Also in the manga you get those kickass faceshots, and punches. Eg when Luffy gets mad and nails Wapol, I think the art is better caus the moment is frozen.
For action scenes, its a bit of both. Sometimes they drag it out in the anime, they move too slow and talk to much (filler parts). But the Luffy vs Zoro fight at Whiskey peak just kicked too much ass animated.
Also about the filler, some of them are pretty bad but some of them are really quite enjoyable. I really liked the one where they showed Zoro meeting Jonny and Yosaku (who I also thought was better animated), and the one where Luffy, Zoro, Chopper get lost in the desert. Although the fillers can create plot holes and discrepencies from the manga, they are still pretty enjoyable.
Also about the voice actors, I think all the Strawhats got perfect VA's so far. I think they do a really good job of bring them "alive."