Jakub was great. He was extremely responsive, friendly and accommodating. The space was exactly as pictured and described -- very clean and sleek, but still homey. It's clearly been very recently renovated. I needed a quiet space that could accommodate my small dog, and this studio was perfect. The kitchenette has all the basics (2 burners, no oven, a microwave, toaster and electric kettle) -- you won't do much major cooking, but it's fine for preparing simple meals.
Although it's in communist-era block housing, it's one of the better maintained developments and was quite cheerful and peaceful (the buildings are only about 4 or 5 stories, so they're not too imposing, and there's a ton of trees and green space surrounding them). For travelers interested in history, staying in a block can give you a bit better sense of what certain aspects of life under communism would have been like. But, as mentioned, the interior is so recently renovated, you certainly won't forget that a quarter century has passed since the system crumbled.
It's a little under a 10-minute walk to the subway, and a bit shorter to a few major tramlines. The area itself is a very good, residential area of Warsaw, and there are a few decent cafes and restaurants within close walking distance (grocery stores literally around the corner). I always felt very safe.
I absolutely recommend both this space and Jakub as a host.