Melias show up in lair, but I haven't noticed them as a big challenge, myself. Prince Ribbit has been moved to Early dungeon, Fanner or whatever that ice wizard's name is, has been bumped forward, seems like two headed ogres are making earlier appearances. There was at least one more unique that showed up surprisingly early for me but i am drawing a blank on who it was.
Maybe it's bad luck, but I've noticed a lot more open dungeon floor plans, more squads of creatures - even groups of squads, more enemies showing up right at the stairwells, and stairwells tending to cluster together when that happens.
The new optional teleport vaults took a minute to learn to handle appropriately (by ignoring them), but larger, more frequent minivaults like larger beehives filled with a variety of opponents are showing up.
It sounds like the changes favor your playstyle. I hate having to kite monsters, stairdance, column dance, and teleport before my health drops below 75%. But even those strategies are weakened by what appears to be a more aggressive respawn rate - and I've always hated having to fight some random monster on a cleared floor while resting. Especially if the monster was a) high level when my health was low, or b) low level when my health wasn't critical. the former is just stressful, the latter is tedious, and IMO, bad design.
I know I am wandering a bit afield of my previous comments, but tedium is a bigger killer of replayability than "lack of challenge" in a game with a 1.5% winrate. Though, of course, tab-smashing can be tedious if you are fortunate enough to have built your character to withstand it and wise enough to cancel when the game throws a genuine challenge into the pile of mooks. I've died many times to a sudden change in difficulty that i didn't notice soon enough.
Finally, I feel I had just gotten decent enough with 0.17 to branch out a bit from Hill Orc Fighters of Okawaru and Deep Dwarves of Mahkleb, or to take either of those into extended. So, the changes are a setback for me, personally, as someone with a grand total of four wins under their belt. After seven hundred games or so. (Hence the "replayability is a null issue" argument I made before. If you are experienced enough to find winning boring, you have either played this game into the ground, played so many roguelikes that it makes no difference, or are some kind of savant.
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Completely unrelated:
Holy Crap! Dungeon level 7. XL 9 MiBe. I have like, 12 unidentified potions and 12 unidentified scrolls. Click the biggest scroll stack (7 scrolls) and yes, lucky me, they are identifies and not teleports. I have a stack of 14 potions - that must be curing. i hope that stack of 6 is heal wounds. Stack of six is curing. What? what the heck? What could that stack of 14 be? Heal wounds?! What the Heck! I've gone entire games with half that many heal wounds (maybe a bit of an exaggeration).