Here's what it took for me to be able to log and flash with the vag-com. Car is 04 wrx, 16 bit ecu.
FTDI drivers, some people have luck with tactrix 1.3 drivers, but not me.
Ecuexplorer, trying to get ecuflash 1.29 to work took forever and it still didn't work. Ecuexplorer worked first try.
I also had to supply 12v to the flash connector as described in subi-bart's thread (listed above).
After that it worked great. I primarily use UTEC for tuning so the vag-com was perfect for me. I only needed to get rid of some choice dtc's and raise my idle for 280* cams. Paying $150 for the tactrix just for that seemed a bit pointless.