Steven and Clair's place was perfect - literally a 5 minute walk from Shin Okubo station, the Yamanote line will get you to Shinjuku station in under 3 minutes. Alternatively, you could walk over to Shinjuku Station (my personal preference, for all the foods along the way) in under 20 minutes. On top of that, you have a My Basket (grocery store) and several convenience stores on the way to Shin Okubo so you can grab a quick coffee for cheap before you're off to take in all the sights.
The apartment itself was sparkling, with amenities a plenty and a shared kitchenette and washer/dryer for your use. Steven is also wonderful to communicate with - despite the last minute notice, he allowed us an early check-in and took time out of his work day to show us around the apartment. He even offered to walk us from Shin Okubo to the apartment which we ended up declining since we were fickle and wound up walking over from Shinjuku station instead.
In a nutshell, perfect location with an amazing host to boot - I'll definitely be looking to book this place again on my next trip to Tokyo (which I'm already planning)!