The apparent improvement because of the recent "surge" has only been brought about because many of those Iraqis, previously labelled "insurgents" etc. are now being paid to act as militia by the Americans
They're integrating security forces in order to more effectively get the insurgency. Given the current unpopularity of coalition forces (thanks to the mess they made when they invaded...), locals are more responsive Iraqi militias who can then help the coalition to beat the insurgency.
The success isn't 'apparent'. It's working. It's not eliminating problems of course, but the evidence does indicate that things are getting at least a little better.
In December last year in Falluja, an avg. of 20 people a day were dying. Which is terrible. But a year before it wasn't uncommon for 100 to die a day (source: The Economist).
It's also seen lower casualties - scroll down and compare military fatalties by month
here.
People also seem to be walking the streets again. Note that there has been a recent spike in violence, and - don't get me wrong, there's still a hell of a lot of work to be done - but the
long-term trend has been a positive one.