As a Mage Main, I'm personally pretty happy. I specifically main Morgana, and just built Frostfang for regen and went to my first item (though Abyssal's getting a cost raise so the 3200 gp "mana sustain + abyssal rush" isn't as strong).
I never used 'any' of the mana items that're getting changed, and the love tap Frostfang took is something I'm mostly okay with. Stops people from realizing there's a perfectly good 850 gp item that fills all your mana needs, so a light nerf I can live with to guarantee it's not in spotlight for a serious nerf later is something I'm okay with.
The slant of the AP items towards quasi utility suits me just 'fine', and Maw of Mal and Merc Scimitar just took a hit, and Spirit Visage's gonna tank a nerf too.
I'm not even worried that Rocket Belt's gonna get to Live, because it's never gonna make it to live in it's current iteration without being Zhoynas'd, and if it somehow doesn't get Zhoynas'd then Morgana's right up there with Annie in the "cheat a flash" abuse category.
But yeah this has to 'suuuck' for most Mage Mids, so I feel for you.