I recently moved a client to PBE. On cPanel hosting he had been using Rouncube as his primary mail client. Roundcube has an option to "Open" an attachment (to view) in addition to "Download". PBE webmail client only offers download, so he needs to download first, then open to view the attachment.

So he moved to a "Premium" mail product & lost that important capability in webmail. Ouch.

With the world using webmail more often I would think this is an important feature to include.