I've bounced off of Forever pretty hard.
My opinion hasn't changed in decades: travel time isn't content. It's just downtime that (nowadays) virtually everyone spends out of game, whether alt-tabed, on a second screen, or on their phone. Whether that's manually traveling to dungeons every time, quest chains that run/fly you right back and forth to town, corpse runs because of too few spirit healers, etc., it's all nothing - it's the lack of a game.
(I will say that one plausible middle ground would be that each dungeon entrance would serve as the discovery point allowing you to use a dungeon stone / LFD tool to get there.)
Layering is bad, bordering on broken, and I'm unconvinced it will be fixed. Apparently, the classic servers have always had these problems and Blizz never fixed them.
Waaay too many zones (especially 30+) have devolved into a person / group camping each individual spawn point because there aren't enough layers. Yeah, people can group up, but it's not a perfect fix either - quest drops don't appear to drop an item per character, meaning grouping does nothing, the grouping tool is still as simplistic as always (a group of 3 can't one click add a group of two), and in the most extreme case, all grouping really does is turn one person camping each spawn point into one group camping each spawn point.
The hyper-spawn rates break linear areas (e.g. caves) as beating backspawns can be very ugly.
The model is based on putting you in the same layers as people you've grouped with - which only works if those people have stayed in the same level / ilevel (for 60) as you have.
Because all timezones are the same server, there are no lower population periods.
For the PVP sadists, you can't actually control territory, since people will just get on a different layer.
The Other Shoes:
1) Blizz has already admitted infinite sideways progression isn't possible, and some future content will have to be straight +ilevel.
2) We still don't have any clarity on what the monetization will be in the future.
Combine those together and Blizz offering paid-for zones with higher ilevels seems a given, with significant negative consequences (devaluing the 'free' (there's still a sub fee) lower ilevel zones, people requiring hard ilevel minimums for group, etc.), depending on just how obnoxious Blizz's prices for new zones might be.
--
While I do expect to get to 60 to see new content (espeically when I'm already subbed to retail), I doubt myself or much of the player base will stick with this once the nostalgia wears off.