It depends on where the flaps are located or if you are using flaperons. For example, flaps toward the tips of the wings will create a loss of control in a stall. Most airplanes have a slightly "twisted" wing to make sure the root stalls first. That way you still have some roll control in the stall (not that you would necessarily want to use ailerons to get out of it. I can elaborate if you like). Flaps toward the wing ends would work against this. Now, if your flaps are properly set up they will allow the pilot to descend at a steep angle without increasing airspeed; however, they are not speed brakes. Because flaps increase both the camber of the wing and the angle of attack by lowering the trailing edge, they allow the same amount of lift to be developed at lower airspeeds. Most often the first bit of flaps add more lift than drag and as you near full extension you get more drag than lift.

Flaps change the center of pressure on the wing and will cause a pitch change. This is why I usually test them well above the ground. Applying flaps may cause a pitch up or down depending on many variables so be ready.