This is one of those 'I like it because it works for me' questions, I'm sure, but who are you using to process transactions? I'm not talking about something like WHMCS or Blesta, or Clientexec, but who you're going through for processors, and why?
My own 0.02:
Industry standard, pretty much if you don't have it, you don't get anywhere... AND their debit card works incredibly well for me (or did up until the past couple of years
). Been using them since 1999-2000 , somewhere in there.
On the card side of things, CDG Commerce
I'll probably end up dropping this, as it's redundant at this point, but I've been with 'em for 10 years, and still do a small amount of card charging on a monthly basis at this point.