I do own Shaco and I've played him for a good amount of time in Season 2.
However, I have yet to play him in Season 3, so I don't really know what it's like in terms of items.
What I can tell you, though, is his playstyle. Shaco is an assassin, focused on killing enemy champions. Shaco can be played as an AD or AP, and both require extremely cautious play. What that means is, to be a good Shaco, you need to have good timing, good map awareness, and smart thinking.
AD Shaco focuses on, well, of course, basic attacks. He uses his skills to assist in attacking continuously without taking much damage for himself. AD Shaco also excels at taking down towers and split pushing, and is one of the best split pushers in the game.
AP Shaco focuses on tricking his opponents and causing disturbances. His main damage comes from his Jack-in-the-Boxes, which fear enemies on contact and deal damage over time. His clone's death also deals significant damage.
I play AD Shaco, just because he is very straightforward and easier to grasp. AP Shaco requires a lot of patience and psychological prowess. I would not recommend AP Shaco to a beginner.