Got a beta invite, finished the campaign, played about 100 ranked matches. In short, I like it!
Haven't spent a penny on the thing, I seem to be genetically immune to micro-transaction stuff - my brain just automatically filters it out. I've played and had a lot of enjoyment out of games with these kinds of systems, without paying anything - spending money is just a way of diluting the challenge, why would I want to do that? I've played some of the most egregiously pay-to-win strategy stuff (Stronghold Kingdoms, I'm looking at you), Card hunter does not in any way fall into that bracket, in my opinion - it's more like a Team Fortress 2-type system - in this particular case you get 2 to 4 random drops after a successful ranked match or PvE scenario, joining the Card Hunter club adds an additional drop. I've picked up some of the strongest items from the NPC shop, just with the gold I've earned over the course of finishing the campaign - I feel there's no need to dump money into the game, as the advantage I could garner at this point from extra items is somewhat incremental. Deck design, decision making and strategy are the winners here, not the cold hand of Mammon.
Some advice from a stingy bastard on what to do with your free pizza slices (you get about 100 from doing the first few scenarios). Don't spend them on chests (argh.. I bought two chests to start with before I knew what was what, I REGRET this decision, can't remember exactly what I got, certainly not worth it). Don't spend them on costume changes (unless that's your bag, no judgement here). Don't even spend them on treasure hunts (I already got one of the sweetest treasure hunt epics as a ranked game reward). The best bang for buck investment for a new player are the multiplayer starter packs - you get a whackload of items - pretty much all common and uncommon, but you need a good item base when you're starting out. I still use a very high proportion of common items in my party, some are very strong choices. So far I've only got the free adventurer's pack party, I'm waiting to see which pack I'll buy next after a few more items - consensus has it that the Fierce Dwarf pack is the strongest for ranked games at the moment, including the excellent rares Rageblood Dagger and Perfect Ferocity. I'll probably go for Holy Healer, mainly for Incense of the Nether Fog and Blessed Ablution.
Important Note: all items you get from multiplayer starter packs are usable in the campaign, and vice versa. The rewards from getting a few ranked wins under my belt helped me power through the campaign, whilst finishing the campaign and unlocking the high level NPC shop (Goblin Bazaar, which becomes available at level 12, I believe) helped me tune up my ranked deck and improve it's performance - in particular, buying a Chillwood Staff for 25 gold turned my dwarf mage into a bit of a monster (encumber mechanics are a little bit overpowered at the moment - sapping the enemy's movement, then dropping them in a lava pit is always good for a laugh).