Almost none. There were some incidental changes from the trap layer, and a few places where code adopted from Vanilla has tweaked things slightly; but there were really no planned changes.

Trying to merge my few changes, made after 1.16 with FA 1.26, so you can probably use them, if you like. I also have plans to seriously revisit monster.txt in "make game harder" manner generally by removing pitifull spells from powerfull monsters.

Wow ... this sounds great. Are you planning on a wilderness map that approximates Beleriand's regions? An unreachable Gondolin?

That's exactly what I'm planning - although High Elves will be able to get to Gondolin. It will be a while before I have anything playable, though.

Well, it seems strange things happen with FA126, It does not work correctly on my linux system, while 116 have no problems at all. It seems it cannot create any file, e.g. cannot save game. Maybe I missed something obvious.

Oh, it seems it can create pref files, just not save. Vanilla 3.3.0 have this too.
trivial solution was to replace ANGBAND_SAVE_DIR with "./lib/save", it seems working now.

It also refuses to run in console mode, at least before I run FA116, it seems some pref files are missing or just deifferent.

Can't wait to play :-)

Btw some wilderness locations seems to be buggy, e.g. going south from Eriador town results in strange things, and gruesome bugz.

I did get a segfault related to race probabilities once (I seem to have messed that up somehow), but my pref files and console mode are fine.

I have just run your 1.26 windows binary.
At first it crashes on start, but second time it runs. Also going south form Eriador results in immediate crush. So it seems not only linux bug.

Fixed now - I had my array indices backwards :o