Hey, all. I just finally took a look at Distrify since I have yet to upload a trailer of my film to my own site – although I only finished my trailer a couple months ago.
One issue I see is that customers need to sign up with Distrify or use their FB login in order to buy. That's why I chose Paypal over Google or Amazon checkout on my site when I sell DVDs: Customers don't have to be Paypal members if they don't want to. It's my guess that a number of people would rather not go through with the transaction rather than have to go through this hassle and risk spam, ID theft, etc. And offering FB login helps, but not if they aren't FB members – which I assume is the case for many of my customers.
A second issue is the inability to configure sales tax. I'd be using this for DVD sales, and this means that while anyone in my home state (CA) who buys from my site would pay tax, if they buy from the widget, they wouldn't (technically, the tax would be included). This is another reason why I had decided to go with Paypal over the other checkout options. They allow you to configure sales tax by zipcode range, rather than just state.
(I should add that if you sell products on Amazon via their Sell On Amazon service, i.e. Amazon Marketplace, they also expect you to include sales tax in your sales price. Of course, that's easier said than done, since only some of your customers will be paying tax, and of those, there may be different rates depending on their location!)