If you are using clientexec, cdg's api won't work, you will need to use auth.net instead. Other than that, I highly recommend them. My turnaround time was about 1 day after sending in my application.
If you live outside U.S the best solution would be online payment systems like : Stormpay, PayPal, E-gold, Neteller. If you live in U.S simply ask your bank about online transactions.