I've previously ordered hundreds (if not up to over $1k) in ESO gold over the last 14 months without any issues. On rare occassions (probably because I ordered so much), it took them longer to deliver the gold (up to 2 days max).
Unfortunately, when I switched games (WoW) I made a small payment for some gold and they were not able to deliver on my server. After some reading, I found that WoW can possibly track large gold transactions and ban accounts, so this could possibly be the reasoning for that.
After a few days however, they refunded my money... which I was not expecting after seeing some of the other bad reviews. They did right by me, and if they have the gold in stock you WILL recieve the product. If they do not, it could take a little longer or they will refund you.