I do believe you'd be very pleasantly surprised with not only the number of players who jumped on during the free play period (holy moly lots! by golly it worked!), but also the amount of Halo 5 players each day and month - this isn't something we've talked about yet, but I am rather happy to share that even before the free play period, Halo 5 has had the highest monthly active players for a Halo title since Halo 3.
Also exciting (and not yet discussed, either) is the increase that H5 has seen in players each month over the past few months (we just got done looking at June numbers, which are once again higher than the previous month). As you can imagine this is pretty darn exciting to see, and this thread seemed like an appropriate place to share this news for the first time
I'd have to get approval from the powers that be to say more in terms of specifics, but you should rest assured that together, we're quite a strong army.