I first bought the blue handle Marples chisels from Lowes and was realitively pleased with them. A little soft but good for the price.
Last year I bought the Two Cherries set. I have not experience the problems that other have (rounded back) I didn't have to do much at all to flatten the back of them and they take and hold a very very sharp edge that have been very durable for me.
I also hear very good things about the Ashley Isles but don't have any experience with them.