I have seen a lot of posts about renting cards on peakmonsters.com, but I didn't have the courage to do it until yesterday.
I had originally thought "it's going to be a waste of money".
But then I hit a wall with Splinterlands. For the second season in a row I was stuck on Bronze II. I had enough rating, but not enough power, to move up to Bronze I.
Given that I was only on c. 1,200 power and needed 5,000 power I knew it would be a LONG time before I progressed upwards.

Renting Cards
It then struck me - I could rent some cards to get more power. I had no idea how to do this, or if it would work, but I thought I would give it a try.
After a few trial and error attempts at working out the mechanics of how to rent (I thought it came out of DEC, not out of HIVE balance) I rented my first card. It was a Level 6 Flame Monkey.
I checked my Splinterlands account, and yes, my power had also increased due to renting this card.
Wow. So I did it again. And I was able to power up and get into Bronze I.
I didn't stop there either - a few more cards and I was into Silver III now having just over 15,000 power. I definately couldn't have done this without renting cards (or spending a lot of money)

Here are all the cards I ended up renting :

Rental Pay Back
I selected my rental cards carefully. I was after higher level cards with a lot of power, that were relatively cheap to rent with little or no escrow fee. I wasn't too worried about playing with them as I was just experimenting.
My 6 rental cards cost a total of $0.008 per day. Over 7 days that is a total of $0.056 - about 56 DEC.
In Bronze II, I was winning about 30 DEC per day, so 56 DEC seemed cheap enough for me - about two days worth of playing before I won enough to cover seven days of rental costs.
I hadn't factored in that in higher leagues you earn more DEC per win. It took just over a day to win back 56 DEC. I was averaging around 3 DEC per match won - initially around 2.5 DEC, but then increasing to 4 DEC (so far). Plus, I will now get more loot at the end of the season.

So for me, the rental has been worth it. I will convert some DEC back into HIVE so that I can cover my rental costs at the end of the seven days (as I like loose ends being tied up), and I will then look to rent some more cards - maybe this time I will choose some cards more strategically for playing with, rather than for powering up.
I would recommend to any Novice, once they have played for a little while to get the game basics, to check out the rental market and dabble in renting a few cards. It does not cost a lot, definately pays back at this level, gets you more DEC to buy your own cards, and increases your loot. And with untamed packs all sold out, it is a good way to widen your monster collection.