I fly only paid F (my own dime). It is long overdue for DL to do this, and I have complained to them about this (excessive recline) for years. Disclosure: I have a major position in DL (DL:NYSE)) and the position has done well (thanks to multiple factors, including mashing more pax into seats).
DL has stacked more seats into its F cabin than the other majors, and I compare my DL flights in the F cabin to what I have seen to my position in the UA and AA's cabins. The comparison between DL and AA on their 737 F cabins is glaring: AA does 4 rows and DL does 5. I fly over 400K actual miles per year and make Exec Plat, 1K, and Diamond on the 3 majors.
DL has had, regardless of how many rows it crams into its F cabin, from long ago had way too much pitch for its F seats. Really bad in trying to get out of your seat when there is only 3 inches distance to get one's knees through. AA and UA are nowhere near this. I suppose if DL wants to cram more seats into the same finite space as its competitors, at least the decent thing for DL to have done would have been to limit the recline of such seats. Hallelujah on waking up to this.
This is a major move that should be applauded. I have always gamed the system by getting bulkhead in F with my wife. We get in line 15 min early to be able to place our carryon's within reach (the first overhead bins have the emergency stuff, so we have to fight for the rest. And don't forget that people weren't rushing the gate to get on with their suitcases until the airlines started charging to check bags).
My worst experiences were on the old DL DC-9's where I'd be in the and row and a guy in row 1 reclined to the max, pretty much burying me. It was usually a large frame guy who must have thoroughly enjoyed his cavernous space. Seldom was a LOL.
Thanks, Delta, for waking up to the obvious. We have been complaining about this a long time. Please don't slip into recidivism and forget to continue this in perpetuity.