In my honest opinion, the only spread sheet I would 100% trust on what mods are in dev is the official FTB one (right
here). Not meaning to offend bigglesworth or anyone, but that one comes straight from the FTB team, who works directly with almost all the mod developers in the FTB pack. Also, on the issue of what the words "in dev" mean, I would assume that in dev means there is a fully or partially working version of the mod on some client or server, not necessarily publicized. All mod authors are in fact interested in updating their mod to 1.5.1, or at least I would hope so because otherwise the mod might as well be taken out of the pack because then it would never be ready for 1.5.1.