Few things to add here:

1. The magical effects you can gain? If you're stupidly lucky, they can be permanent (this water tasted very odd). This can either be *great* (invisibility, polycontrol, possibly even haste), nice (can't smell anymore), or horrid (slow, teleportitis, polymorphitis). The thing IMO that makes it worth the risk is that the good magic effects seem to outweigh the bad.

2. Diseases include: Lycanthropy (every so often you'll turn into a werewolf with generally higher stats but no equipment and only biting as a weapon), tapeworms (after a certain number of turns or so you'll start taking internal damage which can only be cured AFAIK by vomiting until the parasite comes out), and leprosy (every once in a while a limb will fall off; note that if this happens and you go to the healer for help that the removed limb in question will still be diseased, such that if you reattach it you'll be a leper again). There may be others, but I'm fairly sure those are it (although teleportitis and polymorphitis might qualify under certain conditions ).

The friendly creatures you can get by drinking from the fountain are also good candidates for fountain protection.

About #1, permanent affects even bad ones can be removed by eating unicorn flesh. Different colors of unicorns have different effects. All unicorn flesh has bad effects so it is a matter of balance; I'd rather have all my stats permanently reduced, than keep perma-slow or perma-confusion. Other affects you didn't list include ESP, telecontol, levitating, infravision, and confusion

Somewhat of a spoiler.

I believe you can get any state except polymorphed, life saved or searching as intrinsic due to an unintentional feature. This is because permanence is represented in the game by setting the state counter to 65535 ticks (roughly 32.8 hours). If you can boost your counter over this, when it drops back to 65535, the state is permanent and can only be removed by magical means, for instance eating grey unicorn flesh. I have gotten permanent teleport control in a real game twice by eating a horde of blink dogs.

You can get permanent haste from fountains. Also slow. Neither affects the game so much, as the danger system eventually starts to take the state into account when deciding what it is going to throw at you. Of course boss fights are a bit easier/harder.

Permanent invisibility, on the other hand, has big consequences. You can easily escape from many monsters, for instance golems and kaimikaze dwarves. Hit and run tactics become more effective. But you can no more do business in shops and the danger system creates much more dangerous monsters at you to balance the fact that they can't see you. So you not only can, but need to retreat more often. (Of course, only the generation of monsters without infravision or ESP is affected this way.)

A wand of cloning will ONLY clone one item on the floor.

A wand of cloning will ONLY clone one item on the floor. *Was a greedy bastard and tried to clone several items, just to clone his Sol Stones.*

...

Addy (Adaminite?) items will rust like no tomarrow when covered in blood.

I was trying to clone several potions, a scroll of harden material, the sol stones, and a few other stuff.