Very nice. I once made something similar under my table (which is white) after reading that exact tutorial, but have since got a real lighting setup haha.
To add to what jpm said, the key thing is making sure the light temperature is consistent all round. Make sure no other lights are on, and don't use your camera flash. Also, I can't tell from your photo, but the translucent cover of the left lamp may affect the temperature too.
Also, always use a tripod (or equivalent stabilising object).
You should be able to deal with the white balance by tweaking in-camera, but Adobe Lightroom makes things a lot easier if you can get it.
