Yes! Many times yes!

And, as now, PMNW required more miles to upgrade from the relatively cheaper fares, but in contrast PMNW offered more upgrade inventory from the full Y fares. I always liked the system--it seemed fair to me--and was willing to pay the price differential or try to adjust my travel dates to get into WBC, even though you weren't allowed to upgrade further into international FC from an upgrade. This rule sometimes caused me to decide to buy WBC as I might then get into FC TPAC, which was a real treat, although I could never expect to be reimbursed for undiscounted FC fares and I would have been embarrassed to ask.

More recently, I've been resentfully buying M+ and upgrading so far, but when I begin to find that such high fares violate reimbursement rules or otherwise cause issues including during IROPs, then I might as well begin to compare fares and service across all carriers. At that point, I'm pretty sure that DL will not be the winner, either for paid BE, upgraded BE, or coach. I suspect the choice will be between a reasonable but not deep discount fare, possibly upgraded with or without a copay, premium economy (i.e., United), or deeply discounted business on any available carrier. In fact, I've been starting to look at UA/LH/LX, CO, and even AA as well as some of the good Asian carriers through other alliances.

I sometimes wonder how many of the upgraded business travelers have really paid for published M fares versus those who get a much lower corporate-contracted rate that is closer to fare classes that cannot normally be upgraded. I've also been noticing that certain cities seem to have significantly lower prices for TATL and TPAC M fares than the M+ fares I face ex-MSP.