You could certainly argue that Detroit looked a little rusty last night. However, I thought what we saw from Boston was much more telling. For the first time in the playoffs, the Celtics looked calm, determined and confident. For the first time, they looked like a championship team. It had nothing to do with how the Pistons played, but it had everything to do with how the C's carried themselves last night. The interviews with Pierce and Garnett after the game conveyed the same thing.
I think Doc is right - the C's may be a little more worn out, but they really gained something from the last two series. They've been through too much to lose their focus now. Detroit won't sneak up on them and steal game 2 - you can book it.
I won't go so far as to predict it, but it wouldn't surprise me at all if the Celtics wrapped this up in 5 (win-win-win-loss-win).