The third Gray Death Legion novel has a new main faction of interest, the Marik's Free Worlds League. In all the CBT novels I've read the FWL has been a side note at best, so it was a nice change. I guess the GDL could not be always fighting only the Draconis Combine... 

Also, the Big Story of the BT universe is touched on, the first two GDL novels (the Decision at Thunder Rift; Mercenary's Star) were pretty much standalones in that sense. In short: there's much more grand-scale worldbuilding here, in addition to the wonderful and "usual" BT worldbuilding. 

Grayson D Carlyle is a bit of a "I succeed in everything I ever try" character, but not in a way that actually annoyed me. He does grow a bit as a character over the three novels, so that's good.