Okay, so my experience so far:
1. All unique textures for ore have been removed and replaced with the old texture for coal. Not sure if this is a bug or if someone mistakenly thought this would be an acceptable fix for the multiple-adjacent-textures bugs. So now, if you do find something you'll have to hit it to find out what it is. Great idea. Not.
2. Overhead zombies don't dig down to you unless it's the day 7 horde as far as I can tell. I've had a swarm milling about overhead while I was clearing out the upper ends of my mine. Went out there the next day and didn't see any signs of digging on the Z's part.
3. Lode distribution ... may or may not be farther spaced. I don't have enough data to really say one way or another, but with the mining speed nerf they definitely *feel* farther apart.
4. Ore distribution in the lode, one the other hand, has changed dramatically in both RWG games I've played through so far.
In A16, you'd have a perlin worm that extended from bedrock up towards the surface, the ore you were looking for was distributed along the outer edges, attached to the rock face, with gravel filling the core. This meant you could simply shovel out the gravel in bulk, collapsing most of it, and keep all the ore you were really there for in the first place. And thanks to the yield on gravel, losing 50-60% of it due to collapse was perfectly fine. You got plenty of stone/sand out of the stuff you did dig.
Now A17 changes this: You still have the perlin worm structure, but the ore (along with actual rock segments) is distributed willy-nilly throughout the worm. You *CANNOT* just collapse gravel however you feel like it, as most of your ore is distributed inside. Losing half the gravel means losing half the ore now. For bedrock based starting structures, one is forced to cautiously shovel out an area and build scaffolding to get to the top of the gravel without dropping an excessive amount of it. Once you've reached the top, you clear a shelf out and progressively shave it down to bedrock, then extend the scaffolding over. Rinse, wash, repeat until the vein is gone. On the plus side, said scaffolding, if done properly, can serve as supports to the overhead stone structure to prevent collapse, or can serve as the framework for said support system. (ie. I generally do this with wood frames but prefer trussing blocks for vertical mine supports, so as the scaffolding gets extended I end up inserting trussing verticals spaced appropriately.)
Now, all that said... the mining speed nerf combined with the distribution change and the fact that gravel yield has been lowered substantially... every swing you take at gravel is wasted time. Every last one. Gravel has about half or less the yield stone does (ie. converting sand to equivalent units of small rock, hitting rock yields roughly twice the rock hitting gravel does) so you're better off boring through pure stone than you are dealing with gravel.) While boring through stone can be ... boring... you simply get more each swing and there's more of it. Gravel's sole purpose now is to give you the middle finger while concealing some ore you can't tell what it is and simultaneously threatening to collapse and eat it all anyway. But you're going to swing at that gravel because you don't have a choice. You want that ore and there's no other way to get it quickly or efficiently anymore.
Surface rocks are still somewhat decent, but given how few there are, you will quickly end up in a situation where travel time and random sneaky zombies/bears will force you to reconsider the gravel shaft you're avoiding.
Other notes:
A) Mining in question was done with Miner/Motherlode at 4. Our server ate its config the day before I would've hit level 100.
B) Starting at bedrock and digging out is still viable, and, sadly thanks to the gravel yield reduction, something you ultimately really want to do if you're building concrete structures. You're going to need that stone (and a *LOT* more) so get it out of the way.
C) The average distance I've mined before striking random lodes at bedrock has been about 100m so far. Still need to do more digging to see if this is consistent. In both instances, I dug a fairly healthy distance before finding one lode and then found another a short distance away, so they may be clustered together more in A17 than A16... but good luck telling what your ore is. A single lode (or vein, take your pick) may have multiple ores in the gravel chute, so relying on what you see mixed in the gravel isn't terribly helpful. I had iron intermixed with lead the last game, and the gravel only ever gave me lead, even in the 30x30 space that was purely iron intermixed.
TL;DR; Summary:
Ore is still out there. It doesn't look like it did. It's probably wider spaced overall. Getting to it is going to be a female dog due to mining speed nerfs, and then you're going to have to waste even more time getting it out because it's mixed with the gravel. Have fun!