I having been using Gumroad to sell my digital products for a while now, and I've been having a very positive experience.
The website works properly, the product listings look great, and, most importantly, I get paid for the sales I make – which is the whole point.
Of course, Gumroad isn't perfect. I've had an issue with the automatic workflows (that allow you to send automatic emails to your customers) because my name has accents in it; to be more precise, my name uses "ã" and their platform was choking on those.
I sent a customer service request saying I was having trouble with the workflows, and they immediately responded saying they'd look at it. They always kept me in the loop and told me how things were going, gave me an intermediate fix while they were solving the issue and, finally, solved the issue entirely!
As of today, I still sell my products with them.