Yo y'all.  I have X3 Producer and loving it.  But i see the special offer and wonder if it is worth it to me to go for it - so i'm trying to figure out what I would get has, that i don't have.  Is there a comparison table or list of new stuff chronologically, since the last X3 Producer version? 
 

Really too many changes to list. If you buy before years and you get lifetime updates.
 
Have a read of the ezines that come with each Platinum update, all the changes are described there.

There is a New Features section in the help

The answer is pretty much, no. The weight of the features have leaned towards the mixing side than the composition. Nothing for lyrics themselves. The Melodyne integration has really developed, so I guess that could count, and the comping of tracks has changed. Both of these may help get some melodic ideas down.