Does Softwareserial have signal inversion like newsoftserial did? (tx, rx, true)
I'll answer my own question, yes it does: SoftwareSerial mySerial(4, 5, true); works.
Well you can always check the SoftwareSerial.h header file to see if its supported.
Eg, there is no mention of sofwareserial.flush() in http://arduino.cc/en/Reference/SoftwareSerial page but checking SoftwareSerial.h header files, we can see that it is still supported.