Connecting top and bottom SMD component pads using via
I am working on a 2 layer board and the PCB will be a double sided
  job. Some components on the top layer will have exact mirrors on the
  bottom right under them. My question is, for SMD components, can I
  just connect those pads with a VIA right in the center of the pads?


Yes, will the assembly house be happy about it? No. Vias wick solder through them, plus using a stencil will apply the wrong amount of solder for the component because most of it will be in the hole. 

If you do this, let the assembly house know (or if your hand soldering them who cares?) They will probably need to hand solder this component. 


  Does this affect electrical performance or production/assembly in any
  shape or form?


If the signals in question aren't running at the +50Mhz speed then no, a few nH of inductance isn't going to make a difference. Vias might slow down very fast ESD events, if this is the only inductor in the current path which is unlikely. if adding a 10's of nH to the design makes a difference then run a PCB via inductance calculator and parallel the vias or do something else.