I used Aria2 in the past to download ISO's of Linux and FreeBSD. There is definitely an advantage to using multiple sources at once.
On an unrelated note, it would be cool if large HTTP downloads provided a header indicating a BitTorrent source as well. That way intelligent clients could switch to BitTorrent or use both in parallel.
There actually is such an header, based on the Metalink format, and aria2 supports it! Unfortunately, while many support Metalink files, almost no other download manager supports Metalink/HTTP headers.
If you download a lot of files from free file hosting sites like Rapidshare or MEGA, check out JDownloader (http://jdownloader.org/home/index?s=lng_en). Its interface is somewhat ugly, but it makes downloading many files from such sites way easier. It can monitor the clipboard for copied links, and it automatically pops up a window for you to enter a CAPTCHA when it’s necessary. I think for some sites it can even solve the CAPTCHA for you.
They separated out the video streams and audio streams, so now the only 1080p link you can get is video only (and it uses a different ID to the old 1080p videos, so support needs to be explicitly added for calculating the link).
I ended up writing a wrapper around youtube-dl and ffmpeg to download the MPEG-DASH video and audio streams and mux it because of this. It was a spur-of-the-moment hack, so don't expect error handling.
Quick question that I couldn't figure out from reading documentation. Can this download a file from bittorrent and http simultaneously? A number of Linux ISOs are downloadable from http mirrors as well as a torrent.
I had to switch to aria2c for fetching larger from AWS S3 (50-150 MB). Otherwise a small peecent of downloads were slow (in EC2), b/c most other fetchers have really poor retry logic.
On an unrelated note, it would be cool if large HTTP downloads provided a header indicating a BitTorrent source as well. That way intelligent clients could switch to BitTorrent or use both in parallel.