Another quick 2c:
http://www.authorize.net/ and their world-wide sister-company
http://www.planetpayment.com/ are horrible. Actually, they're decent, but I'd never use them, mainly because of the payout schedule. Can take up to 6 weeks to receive funds, plus they keep a 10% chargeback reserve (or at least they did when I used them), which they release every 6 months.
Ends up being a pain in the ass if your business is expanding very quickly, but various things get stalled due to the fact you can't invest your own money for up to 6 weeks.
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