How often do you guys replace your fuel filters? They have a fuel pressure regulator built into them, which can play up. Whilst the rail pressure may be OK, the flow might not be, hence the sluggish starting. I also suspect the mechanical pump needs a little time to build pressure / flow and if the feed pressure / flow is not there on the initial first cold start, it doesn't help matters.
If you're in-tank pump is a little more audible than usual, try bunging a new filter on as it's cheap easy to replace. Mine has always started on the button since I've had it, but then again, I did a *FULL* service on it the day after I picked it up. All filters, plugs, MAF, coilpacks, oil, coolant, all of it. I like to 'start over' when I get a new car as you never know how it was treated beforehand.