Ex-original Op Flash player here. Haven't played a whole lot of ARMA but the word of mouth from some friends, various videos and streams, had me run straight to steam and purchase Arma 2 CO. I think a few people on here really are being modest and downplaying what Rocket's project has done. I understand that you all have your allegiances as loyal ARMA fans, and you look at Dayz as this stripped down, simplified mod version of the game you love, but you're selling a great idea short.
ARMA in itself, is a fantastic sim that offers unrivaled realistic visuals and a massive world to play in, I think the biggest things holding the game back from a bigger audience is the clunkiness and lack of polish in some areas even more than the learning curve that some people seem to perceive as the problem.
Dayz represents a much bigger point than simply whether or not Arma is a good game or engine. For years, the gaming industry has been trending towards more simple gameplay, easier multiplayer... you know the kind, the arcade-y shooter, the MMORPG's that have been so simplified they almost feel like they're on rails now... Dayz represents the fact that the gaming community is ready for hardcore sandbox gameplay that isn't overbalanced into oblivion.
The selling point for people on Dayz isn't simply "zombies" as I've seen people saying. It's the lawlessness. It's the fact that every single person I've encountered that wasn't an IRL friend of mine, we had a tense conversation, and backed away from each other with guns drawn. There is no safety in Dayz. There is no newbie friendly zones or NPC guards. There is you, the huge map, loot that you absolutely need to survive, and people who want your loot.
Dayz offers so much more than zombies. I wish the ARMA community as a whole would understand that. Dayz has singlehandedly pushed ARMA out of being an obscure, small knit community, to the #1 title on Steam over a CoD map-pack that fanboys far and wide are downloading while foaming at the mouth, and 8 other titles, some major Triple A titles that were recently discounted.
I hope that BIS sees what Rocket has accomplished in his free time and truly supports it going forward. With the release of ARMA 3, the new features, and potential features that we may not know about right now, they could turn Dayz into the perfect companion game-mode of ARMA 3 that could help drive sales even further. Look at how many people ran out to buy an ALPHA version of a mod for a game they've never played before. Imagine what you could do with it being a supported, fully developed gameplay mode or stand-alone game? If Dayz offered something like barricading or occupying buildings and towns, you could see an entire player-based barter and trade economy built, tense alliances, warfare, a world in it's own.
For the TLDR crowd, this is my plea for BIS to support Dayz fully going forward, and turn it into the hardcore sandbox multiplayer experience that a segment of PC gamers have been waiting for since the days of Ultima Online and Shadowbane. Something that doesn't exist anywhere else. Please don't sweep this under the rug as simply another "zombie craze". You aren't giving Dayz credit by doing that.