Pros: Like everyone else says, the views are truly amazing. The place is huge. Incredibly clean. Everything is in excellent working order. The building felt very safe. Wifi was fast and worked throughout the apartment. The kitchen was well stocked with cooking implements, utensils, plates, etc.
Neutral: The neighborhood is up and coming. We never felt unsafe, but be cautious walking around alone late at night. A number of good restaurants within walking distance and it's a stone's throw from the Mercato Metropolitano which is amazing. And very easy access to the Elephant & Castle tube station.
The air conditioning works well, but if you're used to a/c in the US, don't expect an arctic blast of cold air. It was in the 90s during the day and the a/c struggled to get much below 80, but at night it was able to cool down into the mid- and low-70s, which was fine.
Cons: The only real con was the check-in process. The arrival email contained zero info on check in. Had to send 2 follow up emails before getting a response that the concierge would have the keys to the apartment. Arrived at the building to find no way to get in and talk to the concierge without a key fob. Called Will who was able to send a concierge out to get us. It worked out fine in the end, but it was an annoying 20 minutes standing outside after a long flight. I think the secret is to just follow someone who has a key fob into the building, but we didn't know that.
TL;DR: Overall, the pros far, far outweigh the cons, and I would wholeheartedly recommend Will's place to anyone and everyone.