Anna's flat is in a great location if you are looking to be a little outside of central London and in a neighborhood. We found it extremely convenient for our trip, which was going all over, not just to the usual London tourist spots. The Herne Hill station is closest but the train there is not the underground. It's not a huge deal, but just something to keep in mind based on what you're trying to do. The underground runs frequently, whereas the trains are on a schedule -- generally every 20-30 minutes. The Brixton station was a 10ish minute walk and very easy to get to. The flat itself is a good size. It's two stories so you can be in separate spaces during the stay if your energies are different (one wants to sleep etc.) The kitchen is... small. It's got everything you need to cook, but it's very small for prepping a meal and the ceiling is slanted under the stairs so it's just uncomfortable to use for longer than a short while, especially if you're tall. This wasn't an issue as we ate out most meals, but figured I'd point it out as it's not entirely obvious in the photos. The bed was comfortable and the shower was great! It was good pressure and temperature, and a good size. Plenty of space to unpack your things though not a ton of space for suitcase storage. We ended up leaving ours downstairs and just unpacking most things for our week-long stay. Overall it has everything you'd need for a short stay and is comfortable for two people.
Regarding the noise other reviews have mentioned.... I found this not to be an issue. It is essentially on a main cut-through road that will get you from one neighborhood to another, so there's not much traffic noise but there is some randomly loud people walking home. The noise does carry in, especially with any windows open. So if you're not used to living on a pedestrian street or having any urban type noise, then this probably isn't the place for you. During the weekdays, noise was extremely minimal -- almost nothing, actually. Weekend nights were the ones with noise (which wasn't even bad), and that's to be expected for this type of road. Honestly, the noise was exactly as expected from a large city neighborhood.
tl;dr -- the location is great! Flat is comfortable for 2 people. Kitchen is fine unless you planned to cook elaborate meals every day. Brockwell Park nearby is very nice, and Blackbird Bakery in Herne Hill had excellent coffee. Nearby Brixton is very lively, great for a night out.