Stripe approves most if not all accounts without underwriting.. People wrongly assume this means their business is "OK".. Stripe then waits until the account begins processing transactions before underwriting.. Oh woops, after proper underwriting/review, your business type is not allowed!
I haven't tried any others (yet). I would be open to suggestions. Currently I only have 3 paying users and I will probably just throw in the towel. I will leave the files online for a long time and let everyone know so they have ample time to migrate elsewhere.
Paymentech. It's a hassle to get started but it's worth it. It's also a lot cheaper than Stripe and you don't have to worry about random account closures.
I'm looking for backup providers as well. I absolutely hate how you have to go to complain on HN (and have the post noticed) to get any support at all from Stripe. What is the hassle involved with Paymentech? How easy is it to integrate like Stripe is? How is it cheaper?
Signed up to Paddle and immediately got flagged as high risk with no explanation. I complained on Twitter and the CEO had a human check us out manually. We're in the process of verification but honestly I don't have big hopes.