FIXED and 100% perfect for the last two weeks. Replaced the home button with the one I bought off the net and it's as good as when I first got it. Works 100% every time I single or double push it.
To me, def not a software issue.
I will make note that when I first tried to re-seat my original home button, I didn't do it correctly. So maybe, just maybe, the original would work with a proper re-seating of the connector, but I'm happy as hell with the results of my replacement home button!
Link to where you purchased the replacement?
I had my phone replaced last week due to this. At first I thought it was dust but I have never been able to shake the feeling that this and the iPad do not share the same home button housing. The iPad just feels very springy and responsive as opposed to the iPhone.