I stayed here recently for 2 nights and I would highly recommend this Guest House.
It represents excellent value, 1100 baht a night from memory. I've stayed in some good 4 star places in bangkok for almost triple the price of this, but I would prefer to stay here.
I found my room to be all that I needed, basic but clean, good bathroom, bed, tv etc. The guest house has a nice garden setting outside, good buffet breakfast and some pleasant common areas. It's a good place to meet interesting people too, and the staff are friendly & efficient.
I enjoyed the location, it's just a short walk to Silom MRT & Sala Daeng BTS and that gives you easy access to the rest of the city. Also, you don't have to walk through the Patpong markets or the nearby redlight area to get to the BTS/MRT . I went those markets once & really hated it. Also Lumpini park is just a short walk away, I love this park.
I'm looking forward to staying here again when I return to Bangkok.

we were there last december 6-11,2011. the place is clean, modest in its amenities but only less than 5 minutes to BTS skytrain and the metro. The free breakfast is good enough to fuel you to bangkok's interesting places and if not there's a lot of street vendors offering food for cheap nearby. Patpong is closeby like 2-3 blocks away where the night market is. Just be aware that you see weird people in patpong though not scary but sad.

I stayed here for a couple of nights while passing through Bangkok for a visa run. Bangkok Christian Guest House is in a really great location, close to the Sky Train and loads of restaurants near by. The rooms are simple but very clean and comfortable. Breakfast consisted of cereal, fruit, yoghurt and a couple of rice and noodle dishes. This would be a great place for families to stay and also for single people. All in all, good value for money.

If you just need a few nights in Bangkok or travelling on a budget this is the place to stay. Rooms are good, clean and spacious. Excellent buffet breakfast to set you up for the day.