After I reconnected the plug on my aux heater, I noticed a small increase in heat. Seems to come to temp a little faster. Not a huge amount, but measurable.
I'm due for a coolant flush; I think I'll back flush the core as well as do the MB flush as recommended, something about citric acid?
EDIT To add, I found this link after posting this...
http://dieselgiant.com/mercedes_citrus_flush.htm
He mentions that his engine temp dropped about 10* after doing the flush, whereas mine normally runs a bit above 90*, not at 100* like others have mentioned. That makes it seem like mine doesn't have much corrosion in it... I'd be interested in thoughts on that, especially if the OP doesn't mine the sideline.