I prefer to board early as I like to get settled in before dealing with any last minute stuff that always seems to occur. And since I don't get to sit in the front very often, it's doesn't hurt to get secure overhead space.
IME, many of these queue jumpers also tend to be middle seaters who want to try to poach a better seat (who often end up having a doubly bad day). I have called a few of them out, usually because they ram into me while trying to push through. Usually get the stinkeye afterwords from them.