If all you are going to use it for is cutting 1/8" ply then get a cheap one.

Where the main defference lies between price ranges is in the recpricating blade. Better modes have adjustment so you can set the blade from cutting straight up and down or in a circular motion to various degrees. This makes an enormous difference in cutting capability. With the blade recipricating, you can cut through 2/4's with the grain easily. They also have dust blowers that blow away the saw dust in front of the blade making it easy to follow your line. Some have a little light too. Better models have a large knob on top making blade changing easy. I had an old rockwell and had to use allen wrenches to change blades and they used to slip loose. The newer variety uses a double knobed top end on the blade which is much more secure. I have a DeWalt with all those features and I never thought they would mean much untill I used the saw a few times and used my brother's cheap one an really noticed the difference. There's lots of good models available these days, but believe me, the recpricating blade option is what seperaties the catagories.

But I have cheap tools too, and they do the job.