Is there functional mainnet already?
Of course, fork already happened, new blocks are being mined (498935 vs original bitcoin 498892), everything is hopefully fine (although last block was more than half an hour ago).
EDIT: all good, 498958 a minute ago.
Do I have to sync all the blocks from original Bitcoin blockchain (80GB+++) before I can mine with Super Bitcoin's qt wallet?
Bitcoin blockchain is 155 GB currently.