The latest aria2 (0.10.0+1) can autocorrect metalink downloads if they contain chunk checksums. Basically, your finished download should have no errors when it's done, similar to rsync and BitTorrent downloads. And it should be pretty fast (depending on your connection speed) by using multiple mirrors.

This automatic error correction is especially nice for ISO downloads, because usually if there is an error in transfer, it messes up the ISO and the full file checksum doesn't match, so you have to download the whole file again (or use rsync or similar).

From Tatsuhiro Tsujikawa, aria2 author:

"As of 0.10.0 aria2 supports chunk checksum in Metalink: it validates chunk checksums while downloading a file like BitTorrent. This gives safer and more reliable download experience.

1) Before dowload begins: Use this to correct damaged downloads. 2) Realtime hash checking: Validate checksum on the fly like BitTorrent."

CentOS metalinks are at http://download.packages.ro/metalink/ (These do not contain chunk checksums yet, but the chunk checksums can be generated with metalink tools from http://prog.infosnel.nl/metalinks/ )