Yes, it is playable (most bugs are fixed pretty good).
And now you can even go into buildings or break them down with tanks and artillery.
But its even getting better in terms of gameplay if you have "operation arrowhead" (which you need for the "cold war rearmed"-mod, as much as i read in the forums for arma 2 - but that seems not 100% ready yet).
Just have a look:
http://www.youtube.com/watch?v=UFCaqMWx6DU
I wonder that no one here seems to loose his head over it, building tons of scenarios about twilight 2000! Its just made for us.
If you have several maps for different terrain, building-, vehicle-, weapon- and uniform-mods you can easily use it as a virtual "Battle-Map" for your T2k-sessions - hmmm, sweet!
Within the editor you can place every unit in a "turn-based"-way, showing the results of movement, battle-damage, and so on.