I got it last year for our WDW trip, mainly for the free bag(s). Now I'm hoping to get enough miles to pay for a trip next year.
First, I see no reason NOT to get it for at least the first year if you're planning on flying Delta, especially if you're travelling with others. For our trip, we checked three bags each way. With the CC, our baggage fees were $0. If we didn't have the card, we would have paid another $150RT. Since the first year's fee is waived, this is a definite savings.
Second, keep in mind it's ONE free checked bag for each member of your party. So if you're travelling by yourself, you'd need to pay for the second bag. If you're with your SO, you'd have to pay for the third bag.
On the mileage thing, we only travel about every other year. BUT, pay attention to the sign up bonus. Currently, it's 30K miles if you spend $500 on the card in the first three months.
I signed up for the card last year. A couple weeks ago I got an email saying I can get 5K bonus miles by referring someone. So I referred my wife. Now she has a card (which now gets us free bags so I can drop my card before the renewal fee comes up).
Speaking of which, if you'll PM me your email address, I'll "refer" you and that could help my mileage if you're willing. You still get the same "sign on bonus", nothing changes for you.
When it comes time for renewal, balance the $95 yearly fee vs. the free bags. If you're taking 2-4 trips, you save $50 for each trip/passenger. Again, we don't fly much, so I was probably going to drop my card, but got one for my wife.