Just a suggestion, make a grimoire, bestiary, or whatever, and include cards. I for one would like to read through the flavor text of the cards, but currently if it's a duplicate equipment at a lower quality than what i have equipped, it is a bit hard to read the grayed-out card with duplicate stamped across it.
Overall, does upgrading the snail speed actually do anything? Coins don't disappear (as far as I can tell), so they will be grabbed whenever the snail gets there. As for coin generation at the tree, the overall % of time in range of it to generate coins remains the same no matter what the speed is. Seems like just a money sink to me.
Endless mode is rediculously easy for the amount of talent points you have by the time you unlock it. How about throwing bosses into there like every 5 minuts, and maybe more than one boss at a time a 20+ minutes.