I used this new service recently in Portland, Ore when booking 2 nights for friends traveling on a road trip. I was able to figure out the identity of the hotel by the description and amenities listed. While it's possible I could have landed the same hotel cheaper through NYOP, booking via Priceline Express offered a bedding choice, which was a very necessary factor in this case (needed two beds). The hotel's rack rate was $95 and I purchased via Priceline Express for $55.

In another case, I won a 4 star hotel for $110 via NYOP when Priceline Express had it for $130 and the hotel's rack rate was $229 for my travel date.

If you're wanting to target a specific hotel, or avoid a certain hotel in the same zone, and you can figure out which property Priceline Express is selling, it can be a good option over NYOP while still saving over booking direct at rack rates.