If you are going to shoot a bunch, you may want to look into a progressive press. MEC still makes a fine machine. There is the 650 model, the Grabber model (9000), and the top of the line is their hydraulic powered model (9000H). You'll ocassionally see them on eBay in 28 ga, but not too often.
If you want the simplicity of a single stage, I have a MEC 600 Jr Mk V in 20 ga, and I can get the dies to convert it to 28 ga.