I've been here many times. The beef shwarma is usually excellent, being juicy, well seasoned, and tender. The chicken is also quite good, properly seasoned and roasted on the spit. The plates and pitas are both well worth it, especially given the price and speed of service.
The felafels are poor, usually undercooked and not very tasty, so don't expect much here. The side salads are typically quite vinegary.
The staff are hit and miss. Some are friendly and generous. Others seem like they can't be bothered and are stingy.
Note that the beef shawrma runs out quickly, so you can't always get it.
Also, it's true that they're not the cleanest place I've seen, often rinsing hands rather than actually washing them. However, I haven't actually experienced any issues with it.
Try it for yourself.