In October 2011, the 20th Anniversary edition of Vampire: The Masquerade was released to the general public. Although the majority of the work is derived from the game's second edition (1992) and its revised edition (1998), a number of alterations were made in the name of clarity and game balance. What were these changes, and where can they be found in the text?
Attributes & Abilities
Character Creation and Costs
I think I can say the major change is the undoing of the metaplot. In V20, Assamites are still cursed, Ravnos are alive and Gangrel dwell in the Camarilla. One of the design objective was to recover the original vampire flavour. It's unclear to me why some other revised changed hasn't been undone, as the Tremere antitribu extermination or the Ahrimanes disappearance.
Apart from that, many mechanics has been changed. I must say that these changes has been openly consulted to the community. Achilli or someone posts for instance a clan description, or a discipline and anyone could contribute with his feedback. Developers still kept the control, but I can say they do listen and include to people's opinion.
Many disciplines has been revised, at least Potence and Celerity. Dodge disappears. Languages are not learnt with Linguistics. Some Dark Ages mechanics are introduces, such as pooled backgrounds or Path of Enlightenment bearings.
I was disappointed that some parts of the book are not changed. Storytelling chapter is pretty much the same, which isn't bad per se, but the Path of Enlightments are the same, except the new Bearing mechanic, which was very disappointing to me as I find the revised edition paths very bad designed.
I have not studied V20 enough to know all the changes, but I expect those examples gives you an idea. As I said, I think the most important is the undoing of the metaplot and the aim to recover the original V:tM feeling, which I feel it hasn't been completely successful.
There isn't a complete list of changes I can find, but the development process is pretty well documented on the development blog, albeit in bits and pieces, and according to this review, the changes are minor at best.