Took it once. Aimed for 1400 and got a 1390, so I spent some time agonizing over the decision to retake because I was sure I could up my quant score. Finally decided that it was probably not worth the effort and money and just left it as that.
Didn't take the psych GRE either and I initially thought this would limit my range of schools. However, I soon realized that most of the places with a good fit didn't require it, and there was only one program which needed it. Turns out that my POI there asked me to apply anyway (and I'm getting an interview ), and that they have accepted people who didn't take the subject test, so I'm really glad I didn't bother with the psych test now.