Brian: There's not an official document highlighting 2.0 to 3.0, but here's a good list, all numbers refer to Version 3.0:
Rules 42 and 43 placed sequentially, to put undercalls, underbets, and underraises together
Rule 43: significant re-wording
Rule 47-A: "...or the player is all-in (Rule 50-B)".
Rule 50: significantly re-worded, with new example to clarify that pushing out all remaining chips silently is all-in if a single smallest chip can be removed and leave the call or more (i.e. it's not subject to the 50% rule). In response to Kenny Hallaert's valid questions on the Version 1.0 and 2.0 language.
Rule57: some re-wording, and "the pot" is defined to include both bets pulled in and bets committed but still in front of players. Also "reasonably" changed to "legally".
Illustration Addendum: Rule 50, Example 4, 4-A, and 4-B
There are some other very minor grammatical changes, but the above are the more significant differences.