Comments on Poster:

1.3m McGraw-Hill Telescope for all data
except May 2009 from 2.4m Hiltner.

You should specify what you assumed for
the magnitude of the host galaxy, since
it is not clearly evident in the May 2009 image.
Subtracting some magnitude probably affects
the post break alpha somewhat, and the unknown
range of host galaxy magnitude should be
allowed to contribute to the uncertainty on alpha.

"Achromatic" means that break time
is identical at all wavelengths,
and so is the change in slope delta(alpha).
Quantitatively you seem to be saying that
they are not identical, because the break times
are different, and the postbreak slopes differ
by 0.3. What about the slopes before the break?
In order to support this type of dicussion,
You should have a Table of alpha and beta
before and after the break, for optical and X-ray,
as well as beta_ox, with error bars.
The break times could also have error bars;
they have too many significant digits in your
abstract.  Then, you have to decide if the
break times are consistent with each other 
given their uncertainties, and if the change
in slope is consistent in optical and X-ray,
before calling the break achromatic.

MDM logo for upper right hand corner:
http://astro.columbia.edu/~jules/grb/graphics/mdmobs.gif

Picture of 1,3m McGraw-Hill Telescope (not 2.4m Hiltner):
http://www.astro.lsa.umich.edu/obs/mdm/pictures/Dscn0126.jpg

I marked a few other minor corrections.