I really like ED, myself. I thought that there were only two flaws:
One - there was insufficient variation between the story lines. Enemies that were more unique at every level and possible giving each line a level all its own would have helped this a lot.
Two - The difficulty was way too low. The two biggest culprits in this are the replenish as you walk magick meter and the trappers. Essentially, if you have the ability to walk around a bit and completely recover after every room, the difficulty should reflect that, or you should not have that ability. Another possibility is that sanity should have been more difficult to recover. My first choice was the blue path, and I actually had a decent challenge on my hands until I learned that a green recover spell heals sanity easily.
Runner up Flaw - the game was too subtle, cerebral, and slow for a lot of gamers. This, I think, has a lot to do with the financial success, and less to do with the quality of ED as a game.
I actually bought two discounted copies of the game (admittedly, it was because I scratched the first disk trying to clean it).
I very much hope to see a sequel to ED, perhaps on the N5. What I would hope would be added to the sequel:
1 - expand the magick system. The magick system in ED was a simple noun-verb (verb and direct object, subject was always "I") matching system with a single adverb (pargon/power). Given this linguistic basis, there are virtually limitless possibilities for expansion. The addition of 1-shot runes would be nice. An interesting, if difficult to implement, possibility would be to make casting disks that have more ways to arrange the runes than just in a circle.
2 - Keep it deep. It's important to grab new gamers, but it won't be ED without the history and depth.
That's all I've got right now.
BG