For anyone looking to lodge their tax online without going through and signing up to mygov, there is a sneak workaround that can be used that I found on whirlpool. Unfortunately I found this after submitting mine. A lot of people in the thread have used it successfully too.
"When you need to put in your mygov username and password (screen 340 for pre-fill, screen 8240 for lodgement), simply enter taxhelp as your mygov username and click the button below (Prefill or Lodge to the ATO) and you will then be offered the verification path used previously in e-tax. You'll then need a Notice of Assessment (NOA) or shared secret details to proceed."
This may change in 2015 however.
Nice share. but why wouldnt you want to register in mygov?