As a bronze player without a huge number of cards, the first day of rentals has been phenomenal. I spent about 50 DEC renting out gold and alpha versions of cards I regularly play for 7 days each, all centered around a fire deck since that is the most common deck I use and easiest to win with.
By far the most expensive was Malric Inferno at 4 DEC/day (I actually messed up and did not realize that the alpha one I rented was on cooldown (that's a lesson, but the early cancellation, I assume means I'll only lose a few DEC - it was a bargain). Most of the others are in the range of 1 DEC/day each.
While an average win still only gives (I estimate) 4 DEC pre-bonuses I'm estimating that I will make all of the spent money back quite easily. And if I continue through the end of the season the additional chests from moving up a rank will definitely make up any remaining difference.
I will still need to see if this gives me the opportunity to compete in some of the bronze tournaments slightly more effectively (now that most of the cards are higher level I think I might have a slightly better chance since I was close to some cutoffs before).
What experiences are others having?
What other cards should I rent?
Should I start playing a different color now that I have access to better cards?