The Witcher-y card game Gwent is still in closed beta, which means you can't play it unless CD Projekt officially invites you behind the velvet rope. You can, however, follow along with the development process, which recently took a big step forward with the addition of ranked matches, a redesigned player progression system, and a pile of new cards.
Player progression will now be measured by "crown halves," which are awarded for winning individual rounds, rather than for match victories, meaning that players won't necessarily come away entirely empty-handed if they do well in a match but ultimately lose. Tiers and reward types haven't been changed, but because of the updated progression system it now takes six crown-halves to fill the progress bar, rather than three outright victories as it used to be.
CD Projekt has also implemented a new experience system that, for now at least, will grant experience points based on your performance in matches. In fine RPG fashion, gaining experience will earn levels, which will bring level-specific rewards such as card kegs or specific cards, scraps, ore, or whatever else the studio decides to toss out.
The new experience system is currently capped at level 100, but lead programmer Jason Slama says in the video that it may be raised at some point in the future if it proves necessary. (He doesn't seem to think it will, though.) Players who were ranked higher than level 10 under the old system will be brought back down to that point (which is where ranked play unlocks), while anyone under level 10 will stay where they were.
A full breakdown of the fixes, changes, and new cards added in this update is available here. At a glance, there are some interesting cards coming in this patch, including alternate Golds of existing cards like Geralt Aard and Yennefer: the Conjurer, and some tweaks to existing cards, especially the Monsters and Scoia'tael.
If you want to give Gwent a shot but haven't yet signed up for the closed beta, you may do so at playgwent.com.