I'm always looking for new tools so I gave this one a test drive. It is very cool and I like the idea of being able to browse the different cloud services in a very nice interface. However, no one doing any reasonable development would find this effective. Having to open a new interface to select a file to upload vs. having a split window where you can drag from a local location is not something to leave out of an FTP program.
By the way, I don't personally use it but I've tried it: the IDE I use (PHPDesigner) has a built in FTP tool that will automatically upload the files when you save them. That might work for some but I like having more control over when things are uploaded.