Beijing Downtown Backpackers is a great place to sign up for the tour to the Great Wall, as they are cheaper than most other places for the same service. They are also employing professional staff who, although they make a few mistakes (in booking errors, laundry items damaged), are willing to give you financial compensations for it! It also provides a free breakfast.
The Beijing Downtown Backpackers is located in a beautiful hutong street lined with fashionable cafes and shops (a bit like in the Soho area of London, but cheaper!). It is a very nice neighbourhood, very safe, and close to the Forbidden City and the parks with lakes. The only downside is the distance from the nearest metro station (well over ten minutes, long if you have a big backpack).
Rooms and Bathrooms
The dorms are shared by four, six, or eight, and do not have lockers but they do have ensuite bathrooms. The showers are ok, except the whole bathroom floor is the shower floor, which means once one person has taken a shower, the floor is wet (and slippery) for the rest of the day. Rooms are cleaned daily. The reception doesn't have enough keys for each room so the doors to the dorms are usually left unlocked. The beds are comfortable and there is air-conditioning (or heating as appropriate). Windows are equipped with mosquito nets.
There aren't that many common spaces, and this is especially felt in the rather tiny living room, just opposite the reception, where there isn't much to do anyway. There is an internet room downstairs with three computers, and you have to pay -- which is quite unusual for China. There is an international phonebox across from the reception (inside the hostel) for which the staff can sell you phone cards. They can also sell you bare necessities items, such as toilet paper (which is not provided in the rooms!), drinks, and postcards. The cafe next door is where breakfast is taken, but during the rest of the day and evening it is a cafe like any other (paying drinks, of course).
The hostel is located in a great little street with lots of cool shops and pubs, and the beds have mattresses thicker than usual for China. However, the hostel staff does make a few mistakes, which is always disappointing -- even if they offer compensation. And the lack of space to socialise is unfortunate, but then you can always go to one of the many nearby cafes.