We (myself and a number of teens) stayed at this property for a full week and had a great time! The unit is very clean, spacious, and is well-equipped with most anything you need (i.e., the kitchen is fully stocked with eating and cooking utensils, there's a washer & dryer, you can use two bikes, etc.). You do need to bring your own sheets & towels (blankets and pillows are provided) and shampoo/conditioner & body soap.
The location is fantastic: easily walkable to the Sea Colony private beach (10-15 minutes max) but you can also take the tram (there's a stop a minute walk away), there are a number of pools close by including one across the parking lot from the unit, and the big tennis complex is just next door. And you can easily get to the Bethany Beach boardwalk by either walking (I'd guess it's a half hour walk), driving (a few minutes), or taking the tram and walking. The teens were able to easily get around without me driving them everywhere, and it seemed safe for them to be out at night on their own.
The host is super responsive (I had a lot of questions!), check-in was a breeze because he communicated everything beforehand, and information about the unit was readily available on the kitchen counter. I would definitely stay again if we head to the Delaware beaches.
P.S. There's an extra $50/person activity fee that you need to pay to Sea Colony directly (when you check in) for use of their facilities.