What are the mechanical differences between L5R editions?

Question

I owned first and third editions, and played a fair bit of first edition. I'm sort of lightly interested in fourth edition, but am curious about what's been changed, fixed, or altered. If the question's too large, I'd settle for the differences between third and fourth and will edit the question accordingly.

Answer 1

Mechanical

• 1st: Roll Stat+Skill, Keep Trait.
  Trait and Ring Cap=5
  Insight= 10x∑(Rings) + ∑(skills)
  All skills narrow. Purchase of skills with skill points is 1:1.
• 2nd: Roll Skill keep Trait.
  Trait and Ring Cap=10
  Insight= 10x∑(Rings) + ∑(skill level-1)
  All skills broad as default. Purchase of skills with skill points is New Level SP for +1 level. Narrow skills optional, add skill level to totals.
• 3rd: Roll Trait + Skill keep Trait.
  Trait and Ring Cap=10
  Insight= 10x∑(Rings) + ∑(skill level-1)
  Most skills broad as default. Purchase of skills with skill points is New Level SP for +1 level. Narrow skills optional, add skill level to totals. Most skills grant bonuses at level 5, many at level 2.
• 4th: Roll Trait + Skill keep Trait.
  Trait and Ring Cap=10
  Most skills broad as default. Don't know the rest, since I've not got the book.

Setting

• 1st is pre-Scorpion Coup
• 2nd is post Scorpion Coup; Supplements drag through the Clan War, 4 Winds, and Ancestor war... essentially the end of the Hantei Dynasti
• 3rd is the Toturi Dynasty...
• 4th - again, I don't know for sure.