I have at least five RTL8188CUS based wifi devices. They are super small, cheap and work fine on any Windows PC. They work at the slow rates reported here on a R-Pi, I see 900 kbit/sec at first and even lower with sustained use. My solution
is to use one with Atheros AR9271 chipset which is still pretty cheap, the specific one I got is $8 on ebay
. I see about 10 Mbit/sec with the Atheros device.