Loyalty no longer worth it ?
DL have made being loyal to them too complicated and not worth it. My wife and I have bounced around between GM and PM with an occasional year of silver. Upgrades have been rare but we get them occasionally. Are rarely able to use companion tickets or other bonuses. Primary benefit has thus been early boarding, small discount on EC TATL, and getting folks in northern MN on the plat line.
AMEX DL Reserve card got us in to Sky clubs (when we traveled together) and a few MQM's, though many years we'd only take the first batch and then switch to Flexperks for the remainder (usually about 9 mos).
With DL flights usually more expensive than UA, fewer direct flights so we get a connection no matter who we fly, fewer upgrades, possibly more difficulty getting status due to MQD's, and now the loss of skyclub access for the 5 or 6 times a year we'd us them, loyalty is seeming too complicated and not really worth it anymore. At least for those of us who don't want to devote gobs of time figuring out DL's and AMEX's systems and what we have to do to get some little scrap from them.