(full disclosure: I am a freelance writer working on Adamant's MARS line, so my comments may be biased. :) )
'Warriors of Mars' is an excellent expansion for MARS. Savage Worlds excels at blending tabletop miniatures action with roleplaying adventures, and MARS as a setting is perfect for the sort of sprawling tactical battles that Savage Showdown does so well.
'Warriors' details combat troops for all the various races in the MARS setting, and includes three tabletop battle scenarios so you can set up and play immediately. The Savage Showdown rules and a custom 'Warriors' Excel troop-builder spreadsheet are even included in the download. The artwork (primarily by Jesus Garcia Lopez) is gorgeous and very evocative. All told, 'Warriors' is a great value for the price.
Unfortunately, there are some spelling and grammar errors which slipped into the final product. Nothing that makes the text unreadable or the information unclear, but it is an annoyance in an otherwise fine product (and the cause of my 4-Star rating instead of the 5-Star rating I wanted to give).
[4 of 5 Stars!]