As a part of the recent Repentance expansion, The Binding of Isaac added Tainted versions of playable characters in order to spice things up a bit. Each one has some heavy downsides that provide interesting challenges for veteran players, as well as a couple of potential upsides that can be expanded upon in order to create some monstrously powerful builds.
Unfortunately not all of the Tainted characters were well balanced, which meant that instead of being a fun extra challenge some of them were just downright annoying to play. So in order to sort that out, as well as fix a gigantic pile of bugs, The Binding of Isaac team has now unleashed Update 1.7.5.
Besides all of the various gameplay tweaks and bug fixes that are far too numerous to go over, Update 1.7.5 has also added 3 new items (Glass Eye, Stye and Mom's Ring), over 200 new room layouts to explore, as well as new Birthright item effects for characters that were still missing one. Combine this with some nice visual improvements like unique starting rooms for every character, and you've got yourself a rather solid update!
If you're interested in all of the details and the exact numbers behind the various changes, and there are certainly quite a few of them, you should hop on over to Steam.
Have fun, and here's to hoping The Binding of Isaac will continue to get fresh new content in the future despite Repentance being the third "final, final, final" expansion.