I recently purchased this phone too and love it. Had a Lumia 1520 before but this phone is better because of the size and does what I need. Would be nice if you could compare the camera of this phone and the Lumia 640
I don't have any comparison pictures unfortunately, but I have done camera tests with both at the same time, and at nighttime/low light, the 640 wins. The BLU's flash can give a blue overcast on pictures when used in those situations. In the day time, it's an adequate camera if you use apps that can help with that. The stock camera is somewhat of a disappointment. In my tests in low light, it is really dark on the front camera. The 640 has more light in it, so it is better in that respect (low light situations), megapixels aside.
My experience with BLU, I have only had problems with Camera360 Sight, but OneShot is nice, just a little slow. I personally wouldn't advise any front camera usage in low light situations, or else you'll see for yourself how much of a nonstarter that is...