I'm trying to install gimp2.0. Here's some output I'm getting:

localhost:/usr/bin# apt-get install gimp2.0
Reading Package Lists... Done
Building Dependency Tree... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.

Since you only requested a single operation it is extremely likely that
the package is simply not installable and a bug report against
that package should be filed.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
gimp2.0: Depends: liblcms (>= 1.08-1)
E: Broken packages

I guess I should install liblcms then.

localhost:/usr/bin# apt-get install liblcms
Reading Package Lists... Done
Building Dependency Tree... Done
Note, selecting liblcms1 instead of liblcms
liblcms1 is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

I guess not. Apparently I have a newer version, but because it has a slightly different name, apt-get isn't entirely aware of the fact that I really do have liblcms.

Short of compiling from source, how do I get around this using apt-get wizardry?

If you are using unstable, the "gimp" package (not "gimp2.0") contains GIMP 2.x now, no need to specify a version-specific one. If you apt-get install something and there are unmet dependencies, it's because there's likely no way to resolve the dependency issue and that a package is broken somewhere because it either depends on something that conflicts with something else somewhere or the package depends on a version or package that doesn't exist yet.

Thanks for the tip regardin the virtual package.

I'm almost there, but I run into this problem when trying to resolve gimp-data (a dependency - also a virtual package).

# apt-get install gimp-data
Reading Package Lists... Done
Building Dependency Tree... Done
The following NEW packages will be installed:
gimp-data
0 upgraded, 1 newly installed, 0 to remove and 336 not upgraded.
1 not fully installed or removed.
Need to get 0B/6129kB of archives.
After unpacking 19.1MB of additional disk space will be used.
(Reading database ... 86711 files and directories currently installed.)
Unpacking gimp-data (from .../gimp-data_2.0.1-1_all.deb) ...
dpkg: error processing /var/cache/apt/archives/gimp-data_2.0.1-1_all.deb (--unpack):
trying to overwrite `/usr/share/gimp/2.0/themes/Default/images/preferences/default-comment.png', which is also in package gimp2.0-data
dpkg-deb: subprocess paste killed by signal (Broken pipe)
Errors were encountered while processing:
/var/cache/apt/archives/gimp-data_2.0.1-1_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

I thought that I could get around this problem by apt-get --purge remove gimp-data and then re-install, but removing it complained that I would lose gimp. So I apt-get --purge remove gimp thinking that when I re-install, it'll be ok. I get no errors, but when I try to re-install, I get this:

# apt-get install -f gimp
Reading Package Lists... Done
Building Dependency Tree... Done
The following extra packages will be installed:
gimp-data
Suggested packages:
gimp-nonfree gimp-python freefont sharefont gimp-data-extras gimp-perl gimpprint-doc
The following NEW packages will be installed:
gimp gimp-data
0 upgraded, 2 newly installed, 0 to remove and 298 not upgraded.
Need to get 0B/9155kB of archives.
After unpacking 27.1MB of additional disk space will be used.
Do you want to continue? [Y/n]
(Reading database ... 86505 files and directories currently installed.)
Unpacking gimp-data (from .../gimp-data_2.0.1-1_all.deb) ...
dpkg: error processing /var/cache/apt/archives/gimp-data_2.0.1-1_all.deb (--unpack):
trying to overwrite `/usr/share/gimp/2.0/themes/Default/images/preferences/default-comment.png', which is also in package gimp2.0-data
dpkg-deb: subprocess paste killed by signal (Broken pipe)
Selecting previously deselected package gimp.
Unpacking gimp (from .../archives/gimp_2.0.1-1_i386.deb) ...
Errors were encountered while processing:
/var/cache/apt/archives/gimp-data_2.0.1-1_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

What's going on with that .deb in my apt/archives, and can I get rid of it in the hopes that it'll re-download and be better?

Nevermind, it seems to be ok after:
dpkg -r gimp2.0-data

All is good.