How gone is gone?

After following this (http://community.spiceworks.com/topic/138965-disk-wipe-software-recommendations?page=3#entry-754879) thread, it sparked a thought.

How secure/effective are these? I've personally used diskpart>clean, quick format, full format & CCleaner's 1& 3 passes to wipe disks. Running Recuva after always finds re-storable files. I've never had time or reason to try CCleaner's 35 pass.

Given Recuva is a lightweight, free app I suspect there are much more powerful tools out there that could restore a lot more.

My question is this - does anyone have experience with something truly effective?

Btw - if this is in the wrong forum, will one of the mods please move it. Thanks! :)