I have many clients scattered around the world - I am based in Poland - and the biggest issue I have is with the US banking system in general.
Pretty much everywhere else around the world, asking a client to transfer electronically to my currency broker's local account (http://currencyfair.com if you're interested) is not a problem. The process is as quick and painless as PayPal, and most times without fee.
In the States though, it's always a different story. Some have to phone up their bank to request a wire transfer. Others ask if they can avoid the wire/PayPal fees and send me a cheque! (I'm astounded that cheques are still being used in 2012). All because it seems that the local banks offer close to nothing for their clients. The concept of using online banking to make a transfer seems to have completely passed the country by.
So, that's what I'd change, and I pray for the day online banking sweeps through the USA as it has elsewhere. I bet PayPal are very much praying for the reverse.