We use our DV for EVERYTHING we possibly can (and pay it off in full every month, of course, or it's not worth it). We put any bill we can, plus use it primarily for everything we buy.
Basically, you get 1% per purchase (2% on some things), so if your grand total on the CC for the month is $2k, you'll get $20 in Disney Rewards Dollars. We average between $20-$40 a month in DRDs

scared: when you think of how much we spend a month!!) One year when we went through fertility treatments, it almost paid for an entire stay at PopCentury! We've been saving for a while, and have about $1500 on it.
I usually use most of it to pay towards the trip around the 45 day mark, then whatever else accumulates between then and the trip I use for souvenirs.
Basically, for us it makes sense, because it's almost a forced saving towards Disney (vs. a rewards card with cash back), but once our kids get older, it' won't be worth it.