Is it worth it to donate in your opinion?
And also lucky.
Yes, it is definitely worth it. There's so much things to do as a donor, the fun never ends.
Yup, lucky.
Jackpots have a 1 in a 600 chance of occurring (I think), unboxing a unusual in TF2 has a chance of 1 in a 100. and I jackpotted 5 times. Holy stuff my luck is amazing.
But I think the jackpots are just free money, because if you just keep on betting 5 you'll eventually win. If you repeat this without getting bored, then you'll have a stuffload of money.
EDIT: Also, I'm on GMTower right now.