@guskooyman and @TombReaper: I actually didn't know what pixel art really is. I see so many awesome pieces of art here that I struggle to believe that they were completely done pixel by pixel. Said this, I can't not love this community! You guys are awesome.
To complete what guskooyman was saying, pixel art is about being aware of how just a little pixel affects your work, an AA tool doesn't give you control on the pixels, therefore it's not considered pixel art. There are two tutorials on the forum, you can check 'em out: A simple but complete one and A really good and detailed one. Take your time and read these, it will help you to understand what pixel art really is (they sure helped me :P) Welcome to PixelJoint.
Always remember, absolutely nothing in pixel art is automatic. Everything is done by hand. Antialiasing doesn't take too long anyway.
Also, if you start your piece with a big brush, don't forget to go back and refine it with a small brush/pencil tool. It makes all the difference.
Thanks for the comments guys! This is just one of my first pieces, I'm very far from being an expert, so any suggestion is really appreciated :)
I made this one with GraphicsGale (that actually I've never used before) and it took just 5 mins. I don't know if there is some automatic way to apply antialias though.
Yea I agree with Tomb, you should put a lot more thought into the curvature of both the head on the right hand side and the shoulders.
I don't want to be rude but this piece is all messy (pixel-wise), this could use some refinement on lines, you could use some antialiasing as well.
Read this tutorial by cure. It should really help you understand pixel art. www.pixeljoint.com/forum/forum_posts.asp
You can also ask around the Pixel Joint forums if you need help with a piece, or if you're having trouble understanding anything. This is a really helpful community.
I also recommend checking out Pixelation. www.wayofthepixel.net/index.php It's another great pixel art community that, from what I've gathered, has a lot of the same members as PJ.
Good luck! I love seeing people get into pixel art, so I hope you stick with it!