Diners Club is my MAIN card.
I signed up for their generally available offer of 3:1 points:dollars (capped at $10,000, first three months), so that's 30,000 points, which convert directly to Qantas points 1:1 thank you very much - with no annual fee or rewards program fee on the first year of the card.
After three months are up, I'll switch back to my 1.5points:1$ card (through a medical organisation, so not gererally available) which gives me 1.5 FF point per dollar spent, so very good!
Okay, so Diners' isn't available everywhere as it costs merchants around 5%, but it's still sufficiently usable to make it easily worth my while. When my wife and I don't use Diners Club, we use the fee-free for life Citibank Gold card - although I am more recent user of that - but no problems yet.
Don't give up on Diners - they're still in the race!