Nothing is more frustrating than PayPal's Sandbox. It's just too slow and initially overwhelmingly confusing. You need to create a PayPal account, then a Sandbox account, then accounts ON the Sandbox account. Whew, that's a lot. Meet Stripe's live/test mode toggle! The easiest way to make sure your payment gateway is setup correctly without much effort.
Stripe is absolutely the easiest payment gateway we've seen. From the smallest projects to the most complicated, it's a huge timesaver. It'll pro-rate monthly payments if cancelled/changed packages, it's capable of scraping a percentage off the top for a parent account (i.e. your CMS charges 1% per transaction from your client's e-commerce store and you can automatically get your cut), and their fees are very fair and comparable to other similar services (2.9% + .30 per successful charge, no other fees!).
Our only real complaint is that it takes a while to get your money (7 days to be exact), however, this is probably going to change at some point, and a new feature allowing you to send payments to U.S. bank accounts seems like it could be used to send payments to yourself? Regardless, that's a really great feature for companies who need to pay their contributors.
If you're looking to start accepting payments, start the right way. Check out Stripe and enjoy their hassle-free integration and each admin panel.
Author: Shane Stebner
Shane is a successful web-developer specializing in responsive design, and the open-source LAMP stack. Over the years, he's gained in-depth experience with Stripe, Twilio, PhantomJs, Authorize.net, PayPal, Facebook, Twitter, and many other plugins/APIs.