I got started on Ultima 1 last night. I went with Gametap so I didn't have to spent a couple of hours to get the game running. I decided not to read any kind of spoilers of hints for it unless I get really stuck. So here is my first impressions:

As expected for a game this old the interface is pretty rough. There is no mouse input of any kind. You move with the arrow keys and have to press different keys for different actions. For example to open a coffin you press 'o' to open a chest you press 'u' for unlock. This is very much like a roguelike and pretty rough. You will need to read the manual to play the game.

There are some confusing things here for people used to modern conventions. There is no resting at an inn to regain HP. You gain HP when you level and by buying HP from the king. The king also gives out quests. 

Food is very important. You need to buy food and make sure you keep plenty on hand. You seem to use less food (none?) in the dungeons so this is where I have been doing most of my leveling.

Overworld movement is tile based sprites and the dungeons have a cool wireframe 3d look to them. They are grid based like Bard's Tale so mapping is easy.

Combat is handled right on the overworld and in the main dungeon view. There is no screen switching and the enemies are visible before they get to you (although due to the technical limitations of the time this is pretty rough underground). In some ways this a level that the JRPGs are only getting to now. There are no 'random' battles, there is no jarring screen transition, and you can see the enemies on the overworld map.

The level of influence this game had on the entire course of RPGs, bot Japanese and Western is immediatly apparent when you start playing the game. The first in game screen you see has your character on the overworld map. There is a castle to the north and a town to the west with some plains, water, and  forest around you. You could up the level of the sprites and put it down right in Dragon Quest 1 and no one would notice.

The quasi 3D dungeon segments with grid based movement had an obvious impact on Wizardry, Might and Magic, and The Bard's Tale. They pretty much made a whole game out of these segments.

No where is the influence of this game more noticeable than Phantasy Star 1 though. Tile based overhead voew land movement followed up with first person mazes, enough said.

So far I have pretty much just bounced back and forth between the first dungeon and the king leveling, buying equip and getting my HP back. The death penalty is pretty stout so I am a bit of a coward until I get stronger.

One more item, some people mentioned to me that I did not mention the Ultima Underworld games in my Ultima game list. I consider Underworld and the Worlds of Adventure games to be different series really and will be handling them seperatly (assuming I can get my hands on working copies).