There seems to be an issue with qb checkouts. Artifacts are stored on QB Server. Artifacts size is about 500 MB.

Our test results (we ran the tests multiple times and :
* wget to the zip download of all artifacts of a build: about 15 seconds
* download via a self written testing java application which just operates like wget: about 20 seconds (also had some different results while increasing and decreasing buffer sizes, but nothing was as slow as QB checkout)
* checkout on agent running on AIX: 45 minutes
* checkout on agent with TAR_TO_DISK system property set to true: 15 minutes

I also attach the test java class I've made: usage:
java -jar jget.jar <url-to-artifact-download> <target-filename> <chunksize-in-byte> <base64auth>

base64auth = encoded "username:password"
Had to do this to be able to have java 6 compatibility without using third party libs.