Does anyone use Gumroad?

It's essentially a sales platform supported by participant fees and a percentage of retail price plus shipping. A quick review of the TOS suggests that caution may be well advised. The lack of participants' commentary may (or may not) be due to what appears to effectively be NDA language within the TOS.

Caveat emptor.

I know people who sell books through it. You upload digital content directly. They will distribute it to people who purchase it. Physical items will be shipped by you, so you would need a stock of them. I've seen people offer things like special signed copies, which isn't something you could do somewhere like Amazon.

Here's an example page for a micropress: https://gumroad.com/stonebirdpress

You will have to handle some aspects of tax, as they don't do everything. This page sums it up based on where you live: http://help.gumroad.com/11164-payments/204243-does-gumroad-add-sales-tax-to-digital-products

I felt it was more hassle than it was worth, given that most customers will buy from established book sites, which handle all sales tax and VAT. My art is also sold through sites that handle all the VAT and sales tax issues. So I've really got no need for a site that maybe does some of it, leaving me with a potential mess of paperwork for the rest. Should such a site spring up that does all the VAT, including physical items, I might be interested. This just seems like something that'd take a lot of work to set up, with few customers actually using it.

I use Gumroad for Ramen Empire. It seems all right. I get my money in a timely manner when I'm running a campaign, and every blue moon a sale trickles in when I'm not.