This is a great plugin, thank you for making it!
Two small bugs in WP 3.0.4: Using the option
checkScript='check.php' prevents the files from uploading. So there is no way to prevent files from being overwritten by a new file with the same name. (I tried entering the full path from /home to the check.php file and that didn't work. I also tried uploading the check.php included in Uploadify 2.1.4 and that didn't work either.)
Also… in Safari I am seeing a message saying There is an error with the upload applet before the Browse button appears. It still functions. In Firefox there is no error message.