Yeah, I'm interested to see how it plays out. Vertical growth is great, but I have yet to see a valid system in an MMO that put it to use in a way that retained players.
eventually people will have all the skills and all the morphs. players and streamers will host guides to get every rare item in the game, and players will be able to hop in and go from A-Z in 1/100th of the time it took us when the game first opens.
I can understand the desire to keep players on relatively equal footing, but at some point it's going to hit a threshold, and without alternatives players will get bored. Horizontal growth is boring at times and can be repetitive, but it's also a cheap way to provide player growth. Vertical progress takes allot more dev time to keep it interesting.
I'm really looking forward to it, but from experience I have my Concerns. When it comes to crafting, I would like to see it have some depth. Perhaps crafting is the way to get the specific bonuses you want, like crafting a cloak that gives fire protection vs. frost protection. or only advanced crafters can swap mods on a piece of gear. so you may get that almost perfect set of mail leggings, but they have the wrong resist, or you were hoping for crit damage and you got mana instead.
But at that point, you have to define what a master crafter is. do they have to have a certain level of expertise to do this? or will I literally be able to start a new character and run over to the dungeon that has the "craft critical damage" skill in it and grab it in 15m? if that's the case then it really boils down to who writes what guides, and crafting will be flat and dead.
And if it becomes a time based thing, then anyone who starts on day one will have a significant advantage over someone who starts 3 months later, and guilds that get big in the first week will always dominate over guilds that start later, unless there's some kind of equalizing element. Time itself is a horizontal progression, just one out of our control.
I think the base problem with vertical progression is it's harder to have a determination of what "progress" means, and how rarity or difficulty fit into this scheme. I see this being less of an issue on the PvP world as it will be on the PvE world.