I'm not sure from your post whether the animation imported successfully? If it has, you can use the Source Engine Exportables to quickly change an Armature's current Action.

I imported as I would any other animation. I expect that either there is a bug in the importer, or there is a problem with my understanding of Blender or the plugin. I can provide test cases for you, if needed.

Edit: I will try to change the Action as you suggested.

Changing the Action did not show the mesh conforming to the animation frame in the 3D View.

This looks like a bug to me, either in Blender or the plugin. I would expect even a one-frame animaion to change the 3D view.

Test case: w_minigun_decompile.7z[drive.google.com]

With that test case, I tried the following steps:
Import "w_minigun_reference.smd".
Import "w_minigun_anims\a_W_MiniGun_AimMatrix_down_center.smd".

I see the frame 0 vertical bar in the Dope Sheet, but unlike what multiple-frame animations show, there are no little circles on that vertical bar (representing bones?). Also, and this is the important part, the mesh in the 3D View is unchanged, even though with that particular animation, the gun barrel should be tilting down.

As a counter-example (a two-frame anim):
Import "w_minigun_reference.smd".
Import "w_minigun_anims\a_W_MiniGun_AimMatrix_TWO_FRAMES.smd".

You might have to zoom in or press Home key in the Dope Sheet to see that there are two frames, both with little circles on their vertical lines. Using the arrow keys while pointer is in the Dope Sheet, you can cycle between those two frames and see that the 3D View shows the mesh changing. The first frame is what I expected to see in the one-frame case above.
(This two-frame SMD file was created by copying the "w_minigun_anims\a_W_MiniGun_AimMatrix_down_center.smd", inserting the "time" section from another SMD file, and changing the second "time" to "time 1".)

Update: I tried the same steps on the latest Blender (2.73a) with the latest Blender Source Tools (2.4.0). Same results as described above.

Has anyone else seen this, or even tried this? Am I the only one that ever looks at one-frame animations? Am I missing something in Blender?

I'm seeing the problem. I'll fix it when I get a chance.

This will be fixed in the next release. You can get the fix on GitHub if you need it sooner.[github.com] You'll need to use Blender 2.74 though.

Thanks, Artfunkel. Much appreciated.

:)