I've had about 10 8x12" enlargements (from 35mm negative)
done over the past 2 weeks.  I'd like to compare notes
with other people who use Costco's *conventional* (not
"1-hour lab") photofinishing for 8x12" enlargements.
I use Costco because they only charge $2.25 USD for an
8x12" enlargement from 35mm neg.

Costco seems to be transitioning its service levels,
because here's what happened:

6 - Kodak DuraLife paper, digitized print (under a
   mangifying glass, the image was obviously formed
   by a digital imager, and not traditional
   'optical enlargement')  No dust or scratches visible

2 - Kodak DuraLife paper, conventional optical
   enlargement (dust, some spots visible)

2 - Kodak paper (generic?!?), conventional optical
   enlargement (dust, some spots visible)

Oh, I submitted 5 orders (each order was for two 8x12"
enlargements.)  Each enlargement came from a different
negative (i did not submit the same negative more than
once.)

I'm guessing the digitized-prints went through Costco's
"Kodak Perfect Touch" workflow.  My original negatives
came back in a cardboard sleeve advertising that service
(you know, the one with the kid and bubble-gum.)

The "digitized" enlargements:
---
The digitized-prints *still* had excessively high
contrast.  4 of the negatives were Kodak Portra 400NC
(which is supposed to be low contrast?!?) These
enlargements looked just like the original 4x6 prints
that I got from initial (regular Costco) film-processing.
A few were Kodak Supra 400, and a few were Fuji Superia
X-tra 400.  The X-tra 400 enlargements appeared to have
the most contrast.  The Supra 400 enlargements were
somewhere between the 400NC and X-tra400 enlargements.

The "conventional" enlargements:
---
Honestly, I couldn't tell the difference between the
Kodak Duralife and 'standard' Kodak paper.  The
conentional enlargements suffered from a few visible
dust spots.  (The digitized enlargements had NO visible
dust spots whatsoever.)

Observations
---
Subjectively, the conventional enlargements were capable
of showing slightly greater detail/sharpness.  I say
'capable of', which implies 'not always.'  All pictures
were shot using a Tokina AT-X 400mm f5.6 (Canon EOS mount.)
I love my Tokina as a great budget lens, but it's
certainly not in the league of a prime Nikon or Canon
400mm lens!  Perhaps I can speculate that a normal 50mm
f1.8 lenses would show greater sharpness differences between
the digitized and optical enlargements.  But Costco's target
audience (folks with sub-$200 point&shoot 35mm/APS cameras)
is already getting plenty of sharpness from the digital
enlargements.

Overall, among the digitzed 35mm enlargements, the
negs from X-tra 400 film looked worst.  The Supra400 looked
best.  Differences weren't that great, though.  Only the
X-tra400's higher contrast obviously stood out.

When I ordered the enlargements, I filled out an order
sleeve.  I reviewed all options in the sleeve-- for 8x12"
enlargements, only the conventional "Costco processing"
is available.  (For 4x6" reprints, you have a choice of
regular-Costco or 'Kodak Perfect Touch.')

Yet it looks like half my 8x12" enlargements went through
the 'Perfect Touch' service, so I don't know what's going
on.  Maybe Costco's technicians accidentally misread
my request.

...

I've used Costco's "1 hour lab" (not available at all Costco
locations) to enlarge 35mm slides to 8x12".  The 1-hour lab
charges $2.25 for 8x12" enlargements (from either negative
or slide.)  The regular Costco photofinishing charges $5
for the same 8x12" (from 35mm slide.)  My Costco uses
a Noritsu console, which scans the 35mm film, then prints
the digitally-captured image onto Fuji Crystal Archive paper.

To me, the Noritsu's output has no visible 'pixel structure'
(which was very obvious on the Kodak Perfect Touch prints.)
But my Costco's console seems to suck in a lot of dust.  All
35mm slide enlargements showed a lot of dust (more than any
of my 35mm negative enlargements.) I also wasn't even sure the
slide enlargements were digitally printed until I looked at
some dust marks under a magnifying glass.  The dust and lint
appear as mercilessly sharp 'black squiggly lines' -- under
a magnifying glass the lines's square-pixels were visible.