I originally tried to purchase one of these digital gift cards through PayPal directly, but my transaction never went through due to high traffic issues on their gift card website.
After 24 hours of waiting and panicking, I finally had my money refunded through PayPal because they had never delivered in their promised time.
Luckily, the Nintendo website also recommended Walmart for the purchase of the eNintendo gift cards, and I was able to buy and receive my code in only 20 minutes.
The reviews were pretty good here and since Walmart also accepts PP, I was able to repeat my transaction much more smoothly and with far better results here, than with the PP site itself.
Sure enough, I entered my code from my email immediately into my WiiU gamepad, and was credited for the amount that I had purchased with no issues whatsoever.
I'm happy!