I think mine took nearly 2 weeks to arrive, I did e-mailed him about 1 week in and he explained his situation, so I was ok with it.
Impressions so far, again I stress these are totally subjective (and biased?), so don't hold me against any claims if you don't see any difference.
Increased hp/torque
Can't say there is, but the car does handle fuel cuts smoother.
Improved fuel economy
So far none observed.
Stabalised idle
Since idling has never been a problem, can't say I've noticed.
Brighter lights
Seems to be a little bit brighter, but without any proper measurements hard to say.
Quicker engine starts
Again my engine always rolled over first time round, so no difference observed.
Reduced emissions
Not measured.
Reduced audio noise
My local radio reception (Northants 96) appears to be better then before, doesn't get overridden by another nearby local radio (Horizon MK).
Disclaimer
Totally subjective, unscientific observations, not properly measured, may be biased.