Does xu4 add any new keybindings to Ultima 4? I thought I read somewhere that an exit key had been added.

Also, how faithful exactly is xu4 to the original? I know it makes some changes (for example, creating mixtures) but I can't find a detailed list. And does it change the difficulty at all if I leave the setting on "Normal"?

Here's some info about additions:
http://ultima.wikia.com/wiki/Xu4

Controls
A - Attack
B - Board ship / Mount horse
C - Cast (Followed by the number of the character who will do the casting, and then the letter of the spell)
D - Descend
E - Enter
F - Fire a ship's cannons (followed by the direction, broadsides only)
G - Get Chest
H - Hole up and camp (may only be used successfully with limited frequency)
I - Ignite a torch (requires torches from guilds)
J) Jimmy lock (Followed by the direction of the door)
K - Klimb (Up by default, use D to descend)
L - Locate position (Requires sextant from that pirate place)
M - Mix Reagents (Followed by the letter of a reagent, one letter per part, with no seperators. Return mixes them. If I wanted to prepare a Jinx spell with one part of black pearl, one of nightshade, and one of mandrake root, I'd type BNM and then press return.
N - New order (followed by the numbers of the characters that you want to switch)
O - Open door (followed by the direction)
P - Peer at gem (requires a gem)
Q - Quit and Save
R - Ready a weapon
S - Search (looks on the ground for unusual items)
T - Talk (You're going to want to say "name", "job", "health", and "join" to most everyone that you meet, then ask about the things that they mention, particularly the nouns.)
U - Use (Uses an item found with the search command)
V - Volume (Toggles sound)
W - Wear armor
X - eXit (Exit your horse, ship, etc and continue on foot)
Y - Yell (Yells "giddyup" or "whoa" to speed/slow your horse)
Z - Ztats (Displays status)

Context-sensitive default actions for the "Enter" key

At the title screen, a configuration menu can be accessed by pressing "c"

Debug/Cheat mode:
To enable it, go from the xu4 main menu to:
Configure => Gameplay Options => Advanced Options => Debug Mode (Cheats)

Cheat list:
- ctrl-c + h (cheat menu help)
- ctrl-d (destroy monster/object)
- ctrl-h (teleport to Lord British's throne room)
- ctrl-v (switch between 3-d and 2-d view; dungeons only)
- F1-F8 (teleport to a dungeon entrance; surface only)
- F9-F11 (teleport to the altar room of truth/love/courage; surface only)
- F12 (display torch duration)
- Escape (end combat; combat only)

Note: Except for the Escape key, none of the cheats work during combat

Thanks. I'm still wondering about difficulty. I understand xu4 changes something about creating mixtures to be more like Ultima 5. I think the only difference is it lets you create several of the same mixture at once.

I found some of the new keybindings:

Alt+H = help
Alt+Q = main menu
Alt+V = version
Alt+X = quit
, = music vol. down
. = music vol. up
< = sound vol. down
> = sound vol. up

The Alt+Q and Alt+X keybindings alone make it much more enjoyable than the vanilla game. Also worth noting that after going to the main menu, pressing J (journey onward) will resume from your previous location but it doesn't actually save the game.

Of course the music is a great addition too. I would enjoy some of the new tilesets, but they seem to be a little buggy. Specifically, the "new" tileset causes a CTD at the gypsy scene in the intro (ref), and the VGA tileset doesn't work at 3x (which is optimal for my screen). Most of all I am just not crazy about how disjointed they look - character sprites in the "VGA-ALLPNG" tileset look very nice, but my character looks different in and out of combat (see attached).

I might play with it for a while anyways to see if I can get used to it.

Turns out your character looks different in and out of combat in vanilla U4 as well, so this isn't necessarily a point against xu4. It's more noticeable in xu4 because the sprites are more different.

A couple other things I decided I don't like about xu4:

* input delay - in the base game you can press the arrow keys like an enraged cocaine addict and cruise over the map at light speed. When you stop pressing the keys, your character stops moving. In xu4, there is some kind of delay, so that when you stop pressing the keys your character continues moving and sometimes doesn't stop until you press the key for the opposite direction. Really annoying.

* bugs - I mentioned bugs with a couple of the tilesets in xu4. I also found a bug where bribing merchants doesn't cost anything, and another where moongates won't disappear. It didn't take long to find these so I'm sure there's plenty more.

TLDR I won't be using xu4. It is hard to give up the music though.