Resume support has been added for all file downloads on StreetDeck.com. You should now be able to resume downloads and do simultaneous multi-part downloads. Tests have confirmed speeds of up to 1.6 MB/s are possible using a home based FIOS connection and a multi-part downloader!
FireFox or another browser which supports resuming is recommended. I also highly recommend using a download helper plugin like DownloadThemAll! that will do a multipart download.
To download StreetDeck 2 or other related files, simply go to the StreetDeck Downloads Page and choose a file.