The great debate about Pluto has, amazingly, remained far hotter than its humble subject ever since it was demoted from full planet status. So, basically, we've had a two year argument about semantics where very intelligent people made fun of other very intelligent people. After which they got blasted at the local pub while arguing how many angels fit on the head of a pin and who had the biggest hands.
I make fun, I know. Now, it must be known that a good definition is a good thing. It would be nice to know what planets, exactly, are. Unfortunately, when you are attempting to define things on a spectrum, as opposed to distinct characteristics, things get squiffy, as we can plainly see.
I was initially opposed to the demotion, and in a sense I still am. Considering the world's astronomers were unable to really define a planet, I saw no reason to eliminate one of the nine we were all taught. I still see little reason for the demotion since a succinct, formal definition of a planet doesn't seem very important to me.
I think it's pretty easy to simply call them planetary bodies and then create arbitrary categories within the spectrum. Say, large bodies are more than five times earth's diameter, etc. The categories themselves are unimportant. I also have a problem with the only aspect of the new definition that is mentioned, namely that a planet is a body large enough to generate a gravity field that squeezes the material into a spherical shape. I have a problem with that because it is physically possible for a planet to be a cube. It's unlikely, but there's nothing specifically preventing that from occurring. So what happens if we discover an object that is the size of earth but more cubic than spherical? It's not a planet?
I like my own definition of a planet. If it is directly orbiting a star and is big enough where we can walk on it without floating off into a very lonely and depressing death, it's a planetary body. If we float off into to space, it's not.
The Great (and Sometimes Serious) Debate About Pluto (LiveScience.com)