When I log to my S3 console I am unable to download multiple selected files (the WebUI allows downloads only when one file is selected):
https://console
In case someone is still looking for an S3 browser and downloader I have just tried Fillezilla Pro (it's a paid version). It worked great.
I created a connection to S3 with Access key and secret key set up via IAM. Connection was instant and downloading of all folders and files was fast.