Wow, I just got this set in today and I'm very impressed. Mostly plastic, but with metal joints--the articulation is just fantastic! Legs swivel and pivot at the hips, knees bend, ankles move somewhat. Head and neck swivel all over. Even the three fingers move. You can replicate most of the typical droid poses, although the fingers' grip is not too tight around the weapon.
You do have to be real careful about "breaking in" the shoulder joints however. They swivel up, but the way it's designed, if you don't have the neck extended all the way up or expect it to just easily move without considering the different moving and non-moving bits, it won't turn correctly and forcing it will break it. It's not necessarily cheap or brittle plastic, but it's light and inherently narrow. Definitely not something you want to be rough with. I didn't do anything bad to mine yet, it's just something to keep in mind if you first start handling it.
Overall, if you love the Clone Wars series as much as I do, you'll want to add these guys to your collection. They look great, are fun to play with, and will complement your clone army nicely. I may pick up more later on, if I can find on sale, or when the inevitable variants start showing up.