Swung by my LGS on the way back from work, and grabbed my copy of RttPtC. I've had a quick look at the player cards, and thought I'd offer some initial thoughts.
I'm not the most experienced player in the world, so take my thoughts with a pinch of salt - and, of course, YMMV.
Guardian
.32 Colt (XP2)
Same amount of ammo, cheaper cost to play, and a free action return to hand ability. An extra icon if you're burning it as a skill card is nice, but the lack of accuracy on each shot still hurts it. A nice back-up weapon, I think, but not your main.
"Eat lead!" (XP0)
I'm a little confused by seeing the basic version of a card we've already got the XP version of, but there you go. As you'd expect, it is more limited than the XP version (has a cost, only gets one extra token), but being able to have some token manipulation for Mark (or other Guardians who prefer firearms) from the get-go is handy.
Seeker
Logical Reasoning (XP4)
Same cost, extra icon, ability to trigger up to 3 times - I think it is a much better recovery card than the non-XP version, but I'm not sure if the cost is *maybe* 1XP too high. Then again, some Seekers seem to run out of things to spend XP on, which this might be handy on - especially if your party features characters with low sanity or mental trauma.
Archaic Glyphs - Markings of Isis (XP3)
I'll be honest, I've not used any of these upgradable Seeker cards, so the value is tricky for me to estimate. Spending a charge to pick up a clue (as I believe the base Investigate clue is still a thing, given the wording on Guiding Stones) and play another asset for free is pretty handy - especially if you're at the spot the Rogue played the Skeleton Key at, and given you only reveal the asset after you've made the check, so you know what you can afford to play.
Rogue
Stealth (XP3)
Becomes a free action, gains an icon. As with Logical Reasoning, it *might* be 1XP too high, but then 3XP stops it going cross-class so often. Most Rogues I've seen haven't had much issue evading things, but effectively getting an extra action a turn is always nice.
Suggestion (XP1)
Another reduced-XP card, this time losing the reaction that saves you from non-Elites, and having a clause that discards it when it runs out of charges. Another one that I don't think is brilliant for most Rogues, though Sefina might want it before she can afford the XP4 version. Has splash potential, though, for characters who have decent Will but low Speed/Dexterity.
Mystic
Alchemical Transmutation (XP2)
Cheaper, extra charge, lower test difficulty, higher potential gain, extra icon (though different to the main one). Quite a lot of bonuses for two XP - or less, if you're running the card that saves XP on spell upgrades. Can gain you 16 resources now, instead of a net 8, though it'll cost you an action more. Feels OK, but would need to test it to see.
Storm of Spirits (XP3)
Same cost, a decent bonus to hit, extra fight icon, deals more damage to your enemies (but also your allies if it goes wrong). I like normal SoS (still want to combo it with DoN off Zoe at some point), so this looks pretty good. Still need to get my head around how the overflow works, admittedly, but I like it.
Survivor
Lantern (XP2)
Cheaper, extra icon, and a remove from game option for a bigger benefit on the discard action. Decent bonus package for 2XP. Whether it is worth it depends on if you like Lantern, but I certainly wouldn't described this as a *bad* card.
Gravedigger's Shovel (XP2)
See Lantern - the Shovel has the same upgrades, and I have the same opinion of it. Still mildy confused how people are using a shovel with just one hand, though.
Basic Weaknesses
Three different versions of Unspeakable Oath, each with a different way of getting rid of them. They all share the Madness and Pact keywords, which are relevant in some campaigns. They're also Campaign Mode only, as their downside won't be an issue for a one-off scenario.
Which oath is worse is going to vary by character. I've played a lot of Zoe, for example, where Bloodlust wouldn't be a problem - but Cowardice would be.
I do like that the drawback isn't trauma, though - having said that, if I was playing Dunwich I think I'd prefer trauma to losing XP!