[This is Julia, the OC]: We started integrating with Paypal and basically gave up because of the engineering effort required. Vs Stripe, which has a great web and iOS app and has been seamless from day 1.
Paypal is one of the hidden mines that await startups - you could have had your smartest engineers working on it for months, possibly sinking the whole endeavor as other (actually important) things fail to get done. Unless you have engineering assets to burn, Paypal is absolutely toxic.