I got a chance today to compare the USM and kit versions of the two 18-55mm
Canon lenses.  They were both the II revision.  I thought I would share the
results since non of the online review sites seems to compare the two lenses
head to head.  I am sure that many would say "who cares" to this but a lot
of people use this lens and some must wonder what the difference is.

They are pretty much identical visually except the lens cap and the USM
label on the front and "ultrasonic" written on the side.  Same size, same
weight (190g), and apparently optically identical.  They use the same hood
too.  Same close focusing limit etc.  The only difference appears to be the
use of a MicroUSM drive vs a MicroMotor drive.

The USM version sells for $139 at B&H and Adorama while the non USM version
adds between $75-100 to the price of a camera body.  Is it worth the extra
$39-64 to get the body only and USM lens separately compared to a body and
lens kit with the non USM lens?  I now think that some people might find
that it is worth the extra money for the USM lens if you are buying a Canon
camera kit and want the 18-55mm lens.

The USM version focused considerably faster with no loss in accuracy or
increase in overshoot or hunting.  They seem to perform identically in the
same situations, but the USM version does it much faster.  The non USM lens
focuses pretty fast, but the USM version is surprisingly quicker.  You can
see the barrel turning much faster.

The USM version is a lot quieter too.  No motor noise is audible whereas the
motor is audible on the non USM version.  The USM lens is not quite silent,
you can hear the plastic barrel turning and extending, but it is very quiet.

If those are important factors, then the USM version might be a better
choice for some.  Maybe the resale value would be a bit better also.