As I recall, Linley specifically designed the original version of Crawl to basically be the anti-Nethack in that respect -- lots of new interesting spells (whereas most of Nethack's spells were just scroll / wand effects dating all the way back to Rogue), little to no need for spoilers, etc.
Between the two I do think Qud is closer to Crawl than Nethack, though. The main thing you have to learn is which enemies are dangerous, and even then, it does have a vague danger readout. There's nothing comparable to Nethack's ridiculous identify-ring-with-sink or scribe-elbereth-everywhere or know-exactly-what-to-wish-for tricks.
(There is the backdoor to the cave leading to Red Rock, I guess. Personally I would prefer making that explicitly visible and having the questgiver direct you to it, as I said above -- I think that for new players, it's a better introduction to the game, since it delays the random variance of overworld travel a bit and lets them encounter the stone-throwing monkeys in a cave where they're less likely to be instantly swarmed.)
Another thing I think Qud would really benefit from is the ability to see the skill screen during character generation (when picking your attributes, in particular.) Maybe even give players a few skill points to spend then, and make it an entire character generation step? They can save the rest for after the game starts or something. The issue is that the attribute cutoffs for skills are
hugely important (especially for True Men), and there's no real way to know them in chargen without memorizing them.
The game plays fair in a lot of ways, though. Golgotha is pretty nasty, but you have a recoiler by the time you go there... maybe there could be slightly more signposts for dealing with Glotrot if you catch it (the bears could reasonably direct you to the mayor of Kyakukya for information on a cure, if you try to talk to one while in an advanced stage of infection); that's the most "guide-dang-it" thing in the game at the moment, I think, since finding the cure mostly depends on you having visited Kyakukya and seen the book before.
(I suspect that some of the people above who find it dull have been playing True Kin. One of the game's major issues at the moment, IMHO, is that True Kin are definitely dull compared to mutants; anyone from the same Arcology and caste is basically going to start out exactly identical, aside from the occasional amazing piece of tech you might start with as an Artifex.)
I got disembowelled by a chitinous puma while completing the quest in the Grit Gate. Can't get how it managed to strike me down just in a single turn. Where can I purchase greater weapons and armor? These beasts lurking all around there seem to be too tough for my one-hand axe, readilly ripping my ring mail either.
In general, you should carry a gun for use on dangerous enemies, even if you're a melee character. You can always buy one in the first town, and lots of early-game enemies carry basic ones, too. Even with no skills, a shotgun blast to the face will help against most things. One thing that maybe isn't completely clear at first is that attacks in Qud can get a damage multiplier if they significantly overwhelm the target's armor, so guns (which have high armor-penetration values) do a lot more damage than it might look at first glance.
(Hrm. That's something else worth maybe making clear to new players, but I'm not sure how.)
Better armor sometimes appears at the shop in the first town, too... or you can travel to the mushroom village past the mountains to the east, although the quest there is harder than Grit Gate, and you're not sure to find anything better there. Also, remember that the shops restock after a while, so you should check regularly. Remember to get boots, gloves, and a helmet, too.
If you're a mutant, you should try to pack a powerful attack mutation like the burning / freezing hands, the stinger mutations, light manipulation, sunder mind, and so on. Alternatively, you can bring an escape option like teleportation, force wall, force bubble, or sleep gas generation.
Some skills help, too, especially proselytize (you can bring an ally or try to proselytize attacking enemies), intimidate, and menacing stare. The shield tree is very good for melee characters if you have very high strength and enough agility to take all the agility options (I think you only need 17 agility?)
Also, it's a good idea to have decent toughness (at least 18), and to always rest until fully healed. A chitinous puma shouldn't be able to one-hit an 18-toughness character at full health unless you're severely underleveled.
(The need to pick your stats might also make Qud a bit more intimidating at first compared to other roguelikes, thinking about it. People with a lot of tabletop game experience will understand that everyone needs decent toughness and that you probably want to max one attribute as high as possible, but not everyone will. Maybe the game could offer a few premade templates to help you learn the game or to let new players get into it quickly -- maybe even combine that with letting people save their own new templates? Hm.)