I used it when I started up my tank and did not experience a cycle as a result. I gradually reduced my tank's dependence over a month and had no adverse effects. 2 months later, I started to see my nitrate levels rise, so I figured I'd put it back in. I haven't seen nitrates since then. I thought my test kit might be broken, but I got an independent test to confirm. Best product ever.
The funny thing is that not all dechlorinators will regenerate it. I'd highly recommend using Prime. I used tetra's aquasafe the first time and it permanently fouled it. Since it's pretty expensive, I don't take chances anymore.