Even though I've recently become known for reveling in excess, I do think the select number of new tiles in this set adds a notable variety of ways to freshen up classic designs. It's not always so much about providing every resource imaginable as it is about consistently using a few of them, and if people consistently use these throughout their designs - for example, making torches a regular feature across their dungeons, or making flowers a regular part of their overworlds - you'll see it doesn't take a load of new tiles or structures to keep things fresh.
Alternatively, inverse-color overworld tiles have been removed. True, they often looked ugly, and while I won't miss them in standard palettes, an argument in their favor could be made regarding their regular usage for snowy areas using CSet 0. Still, even that point is rendered moot given the availability of new winter palettes, so I think it's safe to say good riddance.
On the functional side, item cellars and passageways have finally had their upper rows solidified so that players can't walk across their open tops and exit the screens sideways. This was one of the longest-standing fixes needed in the default template, so it's good to finally have that taken care of.
And though the large amount of new palettes has been the primary attraction, it's also worth pointing out that all of the original Z1 palettes are still mostly supported. Levels 4/6, 5/7 and 8/9 have been combined into single palettes, meaning you lose the unique liquid/statue color of the latter in each case (CSet 3 color 1). Given that the CSet 4 color in the same slot was essentially never used anyway (was it?), I would have replaced it with the second Level 6/7/9 color instead of leaving it as the original third Level 4/5/8 color. And even if it was used in some obscure instance, I would still place primary focus on the color that was used for every statue and liquid across the entire dungeons, because then the main colors of both levels could be represented with a simple CSet switch. But again, it's the new palettes that are the primary focus here, and lingering on the old stuff is kind of missing the point of this set.
All in all, there's plenty of great additions and only a few minor cuts. Far as I'm concerned, anybody who wants to make a classic quest can overwrite ZQ's default classic template with this one.