I wasn't aware wifi was an issue. Looking at the system requirements on their FTP client, it mentions nothing about wifi. But who knows... that may be a pickle. The FTP client lists the only requirement is OS 4.2.1 or greater.
Just installed and tried to use this...all it did was give me a "Device Error" and (couldn't read the # it had because it) made my phone reboot while trying to connect to my server.