I currently use Paddle. There have been some issues with the lack of documentation during the development, but as a developer, I'd rather deal with that than filing taxes internationally.
Gumroad is nicer from the indie developer perspective, less restrictive than Paddle regarding product types sold, but shopping card and pricing are more limited (USD prices w/o VAT only).
Stripe is still better from the developer's standpoint, more mature and nicer integration / API, but doesn't handle tax filing. Would use it if developing a product for a single market.
