The Delta Reserve is a niche credit card. Many won't want to pay $450 for a card that earns solely Delta miles. But the Delta Reserve's ability to earn Delta redeemable miles is not why people should open this card.

The Delta Reserve Card from American Express comes with 10,000 Medallion Qualification Miles (MQMs) for spending $3,000 on the card within three months of opening it.

United, American, Delta, and Southwest are all offering bonuses for shopping through their portals. The bonuses are in addition to what you'd already be earning by shopping through the portal. Shopping portals allow you to earn miles by making your normal online purchases through your favorite online stores. Just by starting at the loyalty program’s portal and using its link to your favorite online retailer, you can get extra miles for your purchases.

With each back to school promotion, the more you spend, the higher your return is.

Through July 12, 2017 (tomorrow) at 11:59 PM ET, you can book roundtrips within the United States (on select routes) for travel September 6 through October 31, 2017 for only 20,000 Delta miles.
Sale Routes
Delta states that the sale applies to award flights with the following origins/destinations:

Washington, DC
Jackson, WY
Bozeman, MT
Idaho Falls, ID
Reno, NV
Phoenix, AZ
Knoxville, TN
Philadelphia, PA
Boston, MA
Salt Lake City, UT
Rapid City, SD
Las Vegas, NV
St. Louis, MS
San Antonio, TX
Buffalo, NY
Sacramento, CA

Flights don't need to be direct.

Tomorrow (July 5, 2017), the Delta Gold card 60,000 mile offer and the Delta Platinum 70,000 mile offer end.

Credit card links have been removed from posts and added to the menu bar at the top of every page of MileValue under the heading Top Travel Credit Cards - Limited Time Credit Card Offers.

Both offers are the highest on record. It’s always important to apply for Amex cards when they have a historically high sign up bonus since you can only get the public sign up bonus on a card once in your lifetime.

In light of the fact that the Delta co-branded American Express cards (both Gold and Platinum) have enhanced sign up offers ending soon (on July 5), a little over a week ago you saw me dive into the reasons why I think SkyMiles are worth collecting.

One of the points I mentioned was for redemption on market standard/cheap economy awards.

On July 5, 2017, the temporarily increased sign up bonus offers for the Delta Gold and Platinum cards issued by American Express will end.
Why SkyMiles?
People like to call Delta miles SkyPesos, me included sometimes, especially when another unannounced devaluation occurs and I'm feeling resentful. That doesn't mean they're worthless though...every mile has its niche, including SkyPesos. And I've put my money where my mouth is. I've held a personal Gold card in the past and currently hold the business gold card.

Delta miles are good for specific reasons.

Until July 5, 2017 the Platinum Delta credit card offers 70,000 bonus miles and the Gold Delta card offers 60,000 bonus miles.

There seemed to be enough interest in my original post on premium cabin award space to Honolulu that I followed up with the next most popular destination in Hawaii: Maui, and will now cover premium cabin award space to Kona (KOA), the third busiest airport in Hawaii on the big island.

The frequent flyer community freaked out over the weekend when expensive fuel surcharges popped on Delta awards flying partner Virgin Atlantic in Upper Class from the United States to Europe.

Delta already collects fuel surcharges on partner awards that originate in Europe.

But out of pocket costs skyrocketed a few days ago to around $500 for Virgin Atlantic Upper Class awards originating in the United States, and everyone thought it was yet another unannounced dig from Delta because, well, it wouldn't be that surprising. Delta devalues their award prices all the time with no notice.

There seemed to be enough interest in my original post on this topic, Who Has the Most First Class Award Space to Honolulu?, that I followed up with the next most popular destination in Hawaii: Maui (OGG airport).