We stayed at the L7 in Gangnam for one night, so our rating is based only off this relatively limited experience. L7 is located in the heart of the business / commercial part of Gangnam, surrounded by sleek high rises. The area is buzzing in activity, especially during the workday. Lots of activities to do nearby, such as the various coffee shops / restaurants, the royal tombs and the massive Starfield Coex mall. Also, as with many parts of Seoul, very clean and walkable.
The hotel itself is super modern and fancy, bordering on the edge of feeling a bit stuck up, but perhaps that it the vibe they are going for. Overall though, the staff are quite friendly and helpful (they even gave us a late check-out option, thank you!). The hotel itself was a little expensive, but again, you are staying in the fanciest neighborhood in Seoul, so you are paying for the location.