So OS X does have a Start button for all intents and purposes, it's just divided into two halves (which basically correspond to the original columns of the XP start menu). I personally feel it would be really annoying to go without either of them.
Once the user accidentally drags it off the dock, it poofs away and they are lost.
Dock pinning doesn't come to them if they don't understand Windows Taskbar pinning, finding /Applications is not a sure thing, and adding items to the Dock is mysterious - they come and go if they're not pinned.
So I've seen people Spotlight apps each time, work out of .DMGs on the desktop, rely on auto-mounted .DMGs from installers (Skype), or keep apps they want around minimized. It's also not rare for them to consider an application "missing" if it's not running and not pinned.
Launchpad + App Store is the answer for this class of user.
That's what I've always used it for. I launch almost every application that way.