This is even harder to review than the original, in that it probably isn't quite good enough value for the price, but fans will still love it none the less.
This introduces two new modes, Legend Mode and Challenge mode. Legend mode has a mixture of stages, with some old, and some rehashed levels from the Vanilla DW, but these each have an emphasis on a particular characters story (although it's not necessary to play as the specific character). These battles generally live up to the title, as I found them to be much more extreme than the battles in the original, with the maps completely chock-a-block full of enemies and officer generals, and they were generally a lot of fun to play.
Legend mode also introduces two of the best additions in the package, and these are difficulty specific weapons (to provide more incentive to play on Chaos, and the new Nightmare difficulty). You get given specific missions to do in-level, and completing these successfully wields much more powerful weapons, which are pretty much essential for unlocking the weapons further down the line. The Nightmare difficulty is the other addition that I mentioned, because it actually makes the game very difficult. This in turn just makes cutting through 3000 enemies and finishing a level without dying feel all the more rewarding.
The challenge mode introduces five different scenarios, such as running through a stage as quick as possible, or killing as many enemies as possible in 10 minutes. It will last about an hour or so, but you will likely tire of it after a couple of runs of each challenge.
In my opinion, however, this game really shines when remixed with the original game. This involves swapping discs for it to import all the modes from the original game. This then allows you to play any of the story mode levels with any character, and also online. It also allows you to tackle all the missions and all of Conquest mode on the newer difficulty, which will certainly take a while if the idea interests you.
It also adds 3 new characters, and some new weapon types, which helps declone some of the characters from the original cast.