Paypal is the best one. But if you own a company, and require a payment processor, use 2Checkout. Also, alternatives to paypal are alert pay, moneybookers and liberty reserve. I've used plimus for quite a while now, its also good, but slow.
PayPal is great and all but in the hosting industry, PayPal cannot be relied on. When a PayPal account starts receiving a lot of transactions over a long time, PayPal begins to limit your account and withhold money. Once my business hit the 10 k a month mark, our PayPal account was being fee'd more and all payments where held for 90 days.
So now I use 2CO and am fairly happy with it. The fees are a bit higher and you can only deposit money once a week, but its reliable. Which is what I care about.
I've heard of that Josh, Paypal started doing a "hold" on a portion of the funds once you hit a certain threshold. I knew of a person running a couple thousand through paypal a month (not much) but because of the type of paypal account he had, when he set it up (i think paypal payments pro) they were doing it. I'm not sure of all the details on that one.