Collected 1.2.0p5 spoilers

[aerol]

This is for players switching over to p5 from older versions and details new stuff since 1.1.1.

Stuff marked with an asterisk (*) has been modified/fixed in later prereleases.

New features

17 new corruptions have been added.
You can now change the font on the Windows version.
* Reading scrolls now sometimes fails depending on your Literacy score (was made more forgiving in newer versions but the behavior still remains).
* It is now more difficult for many classes to learn spells from books, especially at lower levels.

Bugfixes

All artifacts are now randomly available.
The ingot crash bug has been fixed.
Dragon doubling has been fixed.
Monsters no longer kill themselves while in a blind rage.
Choosing the skilled talents no longer crashes the game.
You no longer always fall when trying to enter the rift.
Integer wraparounds have been fixed which fixes many bugs caused by them.

There are loads of others. Check the changelog for a complete list of fixed bugs and implemented RFEs. Everything below "ADOM 1.2.0 Prerelease 5 Changelog (15 November 2012)" applies.

New corruption considerations

"You are attached to chaos corrupting your foes" will fully heal WMoPC whenever a hit connects. I don't know if this applies after the damage dealt; if it does, the only way to kill one in melee with this corruption is to one-hit it; if it doesn't, it makes them impossible to kill. You can also turn enemies into chaos beings with the corruption dealt by your attacks if you deal enough corruption before you kill them; this includes turning into WMoPC. Be careful with this as it will greatly complicate your life if you turn an orb guardian into a WMoPC - see "known bugs" below.
"Your mouth has turned into a writhing mass of prehensile tentacles" will make speaking to NPCs fail most of the time, but not every time. Keep trying if you really need to talk to someone. It will also make spellcasting fail a lot.
"Your bodily tissues seem to be in a state of decay requiring a lot of will to stay up" will greatly reduce your natural regeneration rate, to the degree that it will at times seem to have stopped completely.

Known bugs

* F2-F5 does not change tactics
* Carpenter quest becomes unwinnable if Yrrigs transforms into a WMoPC: this bug affects all monsters (including orb guardians) and because of this under rare, specific and avoidable circumstances it can make a game unwinnable. See this thread.

For a complete list of bugs reported for p5 check this list.
For bugs not yet fixed that apply to p5 but are not included in the preceding list check this other list.
Bugs fixed after p5 but still present in p5 can be found here.

Other related threads

[SPOILY] new corruption effects
1.2.0p5 FreeBSD question re: savefiles