Hi there, new here and just taking a look around.....
Having been to a Hagen Trade Conference/Seminar thingy, the concept behind 'Cycle' compared to other similar products is rather clever.
Based on the principles of competitive exclusion, when added regularly it can actually promote a healthier body of water. It will by no means cycle your tank for you, but will add the bacteria essential to start up this process.
Theres a page about it on the Hagen website, http://www.hagen.com/uk/aquatic/info_sheet.cfm?CAT=1&INFO=43, and the evidence presented at the conference was pretty impressive.
Just thought I'd mention lol.