Uhm... for clearing things up a bit. For sprites and the like you can either use opaque, bitmasked or translucent images. Opaque images have no transparency at all. Bitmasked images have pixels which are either fully opaque or fully transparent. Translucent images have a seperate alpha channel... so you have 256 different "shades" of transparency there.
Ok. That's the one part.
And antialiasing is that stuff used for lines/text etc. It's also some kind of fullalpha, but all those pixels are generated at runtime (and setting that transaccel flag doesn't help at all right now). Antialiasing is really slow if you do it on a frame by frame basis.
Well, if you want to use fullalpha you can use that flag, but you won't get consistent performance across different platforms. Using LWJGL (or JOGL) helps. [If you want lots of blending or rotation opengl is the way to go]
However, most games can look perfectly fine with simple bitmasked images. It really depends on the style you want to achieve and the tricks you're able to use. You can for example make a perfect looking breakout game without using full alpha. The trick is simply using a single color background and have the ball image copied over into a small image with the same color as the background (at the beginning).
So, use simple opaque/bitmasked images at the beginning. Learn the concepts etc and move on.
My first game for example (TC 256 color mode) didn't even had any images at all. Needless to say that it really sucked (as everyone's first game heh