Not counting the "series" cards (brain capacity, energy tank, quoin multiplier & others still to come) or "keepables" (get out of hell free, re-shuffle & others still to come) there are currently a bit over 200 upgrades in the whole deck. But, we'll be adding more.
Can't wait Stoot :) Good to hear! I look forward to the day there are thousands upon thousands of tiny little tweaks you can make to the game experience through the upgrades ;)
Bizzaro Sagan, it seems like they don't stack, but also don't override either. If you already bought the 30% one, the 20% one doesn't make a difference. But not completely sure; if it did override that'd be unintentional since you got them out of order.
I can vouch for the herb harvest stacking -- when harvesting a full crop of purple flowers, I've been coming away with close to 300 with about half of my plots having super harvests
Aviatrix the only way to see cards is to:
1) buy cards with iMG to see what's underneth
2) buy a spin of cards with iMG. you can only do this once a game day