PRO's:
Location is great. Less than 10 min walk from the tube and there's a bus line right in front of flat. We only took the tube during our stay. Get a pay-as-you-go Oyster card immediately as you land from Heathrow. Take the Piccadilly line to Kings Crossing and switch over to the Northern line and get off at the Borough stop. Long lane is a few streets across from the Borough station exit, more towards the left by the little park/sitting area. The flat has everything you'll need, towels, shampoo/conditioner, hair dryer, ironing/board, vacuum/broom, full kitchen utensils, paper towels, hand soap, trash liners, etc. Just bring your own tooth paste. There is a washer/dryer combo. We just laid out our moist clothes as it doesn't fully dry your clothes. Ground level so no stairs to deal with. There's also a Tesci's mart down the street with super cheap groceries and everything else you'll need.
CON's:
Smaller than what we imagined but totally fine for the more budget conscious traveler. Floors could use a good mopping. Mattresses definitely need to be replaced as it's all springs. Shower head will scorch you with hot water if you hold it any other way other than upright. Be careful with that one. Because it's street level, outside street noise can be an issue if you're a light sleeper.
Really, more praises than complaints for this flat. If you just need an affordable place to stay close to central London, this flat is perfect!