The game is quite good. It has been out for a long time and it had patches to address a LOT of the complaints against the original shipping version. I am a huge Supreme Commander / Forged Alliance fan and I was one of the many fans that felt burned by the "dumbing down" of SupCom2 on release.
One PC Gamer UK editor changed it from "good" to his "co-op game of the year" in 2010 after the patches:
http://www.pcgamer.com/2010/12/25/pc...e-of-the-year/
Post-patch(es) steam says I've put 192 hours into the game, almost exclusively in the form of skirmish/co-op/etc. So, I feel it is a great game now and it is a total steal at $5... if you like RTS at all don't pass this up.
NOTE: The DLC Infinite War is pretty much a must-have it adds a LOT to the game in terms of units, maps, tech, etc. It is also on sale.