I think it's my favorite mode, using the Govt + AUC vs FARC + Cartels method with no bots.
I still really enjoy solitaire and four player, but I am very surprised that I am enjoying the two player game so much.
Currently. in the middle of my second game now. The first time was very brutal, as my opponent was able to set up a nice sequence early in the game to pretty much lock down the Government from doing anything effective. I chalk that up to a learning experience for me though. This game is going much differently. You can really work some nice combinations with Eligibility Matrix and the card effects.
I probably prefer the 4-player game as the uncertainty of what another faction may do creates a lot of tension, but the 2-player game is excellent as the synergy created by controlling two factions creates some very interesting play opportunities.