After a single day of playing, getting to level 5, and watching some videos on Youtube regarding it before hand, my initial impressions -
It's fun, and has a different base mechanic than most CCGs. In this game, you play cards, one at a time, back and forth with your opponent, trying to get the most strength (combined from all units on the field) for a round. Naturally there are lots of effects and spells you can play that modify things. Each match is best 2 out of 3 rounds. You can choose to pass for the rest of the round at will, and your opponent can either go on playing (if they're behind and want to catch up), or concede the round by passing themselves.
Free to play is definitely viable with rewards you get from higher ranks once you can get into ranked play (level 10). Crafting good all around cards early on should get you through the low ranks with a solid win percentage.
Cards are limited in decks by their border - bronze cards may have up to three copies, but silver and gold cards can only be one per deck. The difference between silver and gold is that gold cards tend to be immune to other effects (almost all effect cards say "non-gold" on them), and you can only have 4 unique gold cards in a deck, while you can have 6 unique silver cards. This mechanic doesn't affect rarity, only gameplay and deck-building (these cards do tend to be rarer, though).
There are 5 factions, each faction has a unique ability. The Monsters one is broken, the Sociatel one is almost as broken, two are decently balanced and one is shit. Besides your faction, you also have a Leader card with their own ability you can use once per match, in lieu of playing a card. Right now, the 5 factions have 3 leaders (each their own card; you begin with a base leader for each faction).
Monsters are kind of ridiculously strong, especially early on. The starter deck starts you with enough decent cards that it's almost head and shoulders better than the rest of the starters, especially when combined with their faction ability. Other factions aren't really combo-y, in general, but require more pieces to work, particularly Northern Realms. I've naturally tinkered with it some, and fitted it in with my general gameplan of "play shit with big numbers", which is all you can do at this level. :p
I'm quite a fan of card games in general, and after kind of dropping off from Elder Scrolls: Legends, I hope I can keep up with this one more and I'm hoping to be at least decent, if not good. My GOG username (needed one for the beta) is now TheRedArmy21. Come drop by and play me if you like.
EDIT: Left a sentence unfinished.
Saving for later when I did or replace my drunk gaming computer. I loved playing Gwent in witcher 3. Still do. Didn't know a stand alone game was made.