I've not had any issues up to date however I've heard many other horror stories, and so I'm sitting and waiting for the worst to come. Till that day comes, I can't say I've had any problems.

I saw this link in my twitter feed (https://stripe.com/) and while it's not paypal, it seems relatively easy to integrate, though if I were a customer I'd probably prefer PayPal since it's much better known and there's the added bonus of not having to give your card details.

Since your client has paid you back the money, I'd let it drop so long as it doesn't affect your future payments and clients.

Good luck getting it all resolved.