RE: Williams firesight
I just picked one up and bolted it on last week. I know that most I've spoke to about the sight use both and swear by them.
I sighted mine in at the range for the first time recently and found that the front sight is too high. I run out of adjustment at the rear sight as a result of the high front bead.
So I now have a HiViz fiber optic front bead sight on the front and the Williams adjustable rear on the back. Looks good, less filling and the turkeys taste great. Less filling... tastes great... Williams sight, yup, it's all good.