This module is improved and extended successor to Version Control For Text Fields. It handles everything it's predecessor did -- providing basic version control features for page content -- and quite a bit more. Download or clone from GitHub: https://github.com/teppokoivula/VersionControl.
This module requires ProcessWire 2.4.1 or later, mostly because of the file features, which require certain Pagefile and Pageimage methods to be hookable. There's no sensible way around this limitation; for those stuck with < 2.4.1, Version Control For Text Fields will remain a viable option.
What does it do?
While editing pages, fields with old revisions available show up with a new icon in their header bars. By hovering that icon you get a list of available revisions and by clicking any one of those the value of that particular field is reverted to that revision. No changes are made to page until you choose a revision and save the page, which means that you can keep switching between revisions to get an idea what's really changed without inadvertently causing any content to change.
The module also adds a History tab to page edit. This tab opens a view to the history of current page in the form of "revisions" -- each of which is a group of changes to page fields processed during one page save (similar to revisions in various source control applications). There are three actions you can perform on these revisions: adding comments, live previewing what the page might've looked in that revision and restoring the page to specific revision.
One specific feature that has been a big thing for me personally is support for file (and image) fields, as the original version control module felt rather incomplete without it. I'm hoping to take this a lot further performance, stability and feature wise, but as it stands right now, it's already included here and should be fully functional.
Watch the video preview here
I prepared a little screencast outlining most of this: http://youtu.be/AkEt3W7meic. Considering that it was my first screencast ever, I'd like to think that it wasn't that bad.. but I might give it another shot at some point, this time planning a bit before hitting "record"
Upgrading from Version Control For Text Fields
For those already using Version Control For Text Fields, I've added something extra. If you upgrade that module to it's latest version, you should see a new checkbox in it's settings screen saying "Don't drop tables during uninstall". If you check this, uninstall the module and then remove it's files (this is required in order to install Version Control), your old data should be automagically imported to Version Control.
Import has only been tested with limited amounts of demo data. Proper tests are yet to come, so please be careful with this feature!
Update, 21.6.2015: as of today, this module is no longer in beta. While all the regular warnings still apply (making changes, including installing any new modules, on a production site should always be considered risky) Version Control has gone through pretty extensive testing, and should be as stable as any other module out there.