I've tried them all out in the name of desktop support, and webmaster support later on. I've used ftp directly from the command line since forever (both on DOS and Unix), so nothing phases me with these clients. I got a licesnse for CuteFTP and keep it around. I recently tried the FireFTP extension for Firefox, and was impressed. it's easy to navigate, keeps a server list, and has advanced functions, like doing directory diffs, so that you can save bandwidth by only updating files or uploading files that are different, etc.
Most good programmer's editors have a built-in FTP function that's nice to have. You can make changes and upload it with a keystroke or two, without opening another app....
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