Actually I had those exact strips, because I wanted to test my water for hardness and alkalinity, and found the nitrite, nitrate, and pH tests to be fairly accurate. I even did a side-by-side comparison with my liquid test kit. They're not bad, but the liquid kit is still better by a long-shot since it lasts a lot longer.
Stay away from the ammonia test strips though. I've used those and the results are very inaccurate.