As of yesterday, I mined $25usd of ZCL after the $1/day electricity cost with a single z9 @ 650mhz.

Assuming there's a price rise in crypto across the board similar to the rise in difficulty, that's still paid off around the end of september, early october. Once batch 2 ships late august, september could see below average returns, extending that out to maybe november, but we should be seeing much better crypto prices by then as well.

So to me "worth it" can be defined as anyone who thinks getting their money back in 4 months is ok.