I don't know anything about the private foundation, but here are some interesting facts:

$930M cash value

Effective tax 40% (for many with state and local tax, this would be as high as 50%)

Your prize is $558M after tax.

However, IF you win, it is actually unlikely that you are the sole winner. Assuming 500M tickets purchased, the odds are:

0 winners 18%

1 winner 30.9%

2 winners 26.5%

3 winners 15.1%

4 winners 6.5%

5 winners 2.2%

...

where each of these is calculated (N choose w) * p^w * (1-p)^(N-w), N = num tickets purchased, w = num winners, p = probability to win jackpot

So, if you win, we know the 0 winners case didn't happen, but each other outcome is still possible. So divide each probability by 0.82 to get the probability of that outcome, given that you win.

We find that, assuming you picked the correct numbers, your odds of being the sole winner is a surprisingly low (at least to me) 37%. Still the most likely number of winners, but a dog to actually happen.

Your average payout, given that you win, is $349.6M.

Considering only the big jackpot, this means that each powerball ticket is a piece of paper worth about $1.20. Factoring in the other prizes, it's worth about $1.40 (estimated).

If, like me, your marginal tax rate would be more like 50% (7% state and 3% local), the average value of a ticket drops to $1.18.

Good luck everyone :)