I find my favorite use of GNU parallel is as a parallel drop in replacement for xargs.

BTW, bzip2 has been obsoleted by xz and the parallel version is called pxz.

xz is clearly superior in many regards. My understanding is that xz can use significantly more memory upon compression/decompression.

http://pokecraft.first-world.info/wiki/Quick_Benchmark:_Gzip...

Some additional discussion about why xz is not as widely used: http://stackoverflow.com/questions/6493270/why-is-tar-gz-sti...