A beautiful choice!
We spent 5 nights at Discovery in late April/early May. I would highly recommend this resort as a Honeymoon destination or just for a relaxing vacation. St. Lucia tourism in general seems to be made up of 95% honeymooners, but couples on vacation will certainly be comfortable. We saw not one child during our trip, I would not recommend St. Lucia as a family destination.
Once you arrive in St. Lucia, do your best to hustle to the front of the immigration line. The officers there are in no hurry, and those in the back of the line faced a long wait. Discovery will arrange a taxi to the resort from the airport ($70 USD charged to the room, tip not included). The ride is about an hour. Everything others have written about the roads is true; there is a hairpin turn every 50 feet. At least the roads are paved (mostly). Since cabs are not cheap, I would seriously look into taking a helicopter or a water taxi to and from the airport. Definitely take a water taxi if you decide to visit any of the other cities around the island from the resort.
The hotel itself is really lovely, very modern and packed with amenities, like Kiehl's products in the bathroom. We had a standard room which we thought was generously sized (the bathrooms are huge). Some people we talked to who had suites commented that the A/C only worked in the bedroom so they spent most of their time there. The plunge pools are not very private, even on the high floors your neighbors are still near. All of the food at the resort was good, the breakfast buffet was very nice (and included in the room rate). I agree with others who have said they are trying a little too hard with the food, it can be overly fussy. The service was very good everywhere at the resort.
There is a free ferry to shuttle guests from the resort to the various restaurants around the bay. Our impressions:
JJ's: good, very cheap food. Stop by for lunch and order whatever is fresh that day.
Rainforest: pricey and trying way too hard. The atmosphere is lovely and I think it's worth it for one dinner. Definitely make a reservation.
Doolittle's: we just had a few drinks here, so I can't comment on the menu. A good place to watch the sunset.
Chateau Mygo: excellent cheap food. The pizza is amazing. Walk from the resort, no need for the ferry.
The resort was not full when we were there, which had advantages and disadvantages. It was nice to have our choice of pool chairs and dinner tables, but many of the excursions were cancelled because minimum person requirements were not met. They will of course arrange private tours for anyone, but it is more expensive. You can get away without ECDs, but it's helpful if you intend to pay for anything in cash. Everyone accepts USD, but you're subject to an off-the-cuff currency conversion. All restaurants we visited accepted credit cards.
We had an excellent snorkeling trip with another couple captained by Guy out of Bateau Mygo. It's easy to arrange these types of trips for half or full day, or for sunset cruises.
The "beach" is public and not pleasant, in my opinion. Stick to the pools at the resort. The grocery store in the marina village is great for picking up a snack or a few cheap beers. Our only excursion was to snorkel, the resort is so relaxing and lush it's hard to leave.