No personal problems with them, but I found it unsettling that despite repeated attempts to report a what I considered a rather severe vulnerability in one of their services a few years ago, I could get no response from them.

It was more of a privacy problem than a direct monetary one (able to view the registered address for any user given their email) but this made it clear to me that they had some serious problems with security.

I continue to use them to make payments as a user, but prefer not to trust them with access to my full bank account. As a business, I'd avoid them if there was a reasonable alternative.