I went into this in detail on the DL forum thread, but:

- Perkchoice is being COMPLETELY ELIMINATED. DL's Pay With Miles is a CREDIT CARD benefit and is the inferior imitation for the NW's credit card benefit where $100 off certificates could be purchased for 10,000 miles each and redeemed for tickets that earned full RDM, EQM and were upgrade eligible. DL's Pay With Miles requires up to 25,000 miles for $100 off, and tickets receive no RDM, no EQM, and no upgrades, even if only $100 of a $500 ticket is purchased with PWM.

- Plat Companion Upgrades are being COMPLETELY ELIMINATED. DL's 12-hour upgrade window is the equivalent of NW's Plat/Gold at-airport upgrade benefit, except it's available to Silvers, but not on the three lowest fare classes while NW's Plat/Gold benefit was good on any fare class.