I knew it existed but I had never bumped into it at a show or wargames show and by the time I tried to buy it on-line it seemed to have 'long gone'. So I kind of snapped it up when I saw it advertised on eBay. Reading the bumf I see that it is officially termed Command Decision 4.1 (dated as 2012) because it is a re-edit of the first production run. Good enough for me (see below):
Glimpsing through it says there is lots of extra stuff to download from the web-site (stats charts and scenarios). A few of the core mechanisms I was happily reading about in CD3 seem to have been surreptitiously dropped. In no particular order. Turn time seems to have gone from 15 to 30 minutes. Rather than number of hits to kill it seems better troops are harder to kill. Spotting goes deterministic. Artillery suppression rather than casualties is a "new" concept.
All I want to make sure I "play some games with it" rather than just add to my collection of wargame rules ;)