For what it's worth, this was recommended to me so I am returning the favor.
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After using it, it is worth the $30, but if there is a cheaper model that looks the same I think it would be fine.
I only use it when I move plants around, re-pot, or if they start looking cooked. Haven't seen the cooked part since using it. Hold it at the plant tops and it gives you a reading. I don't do light science so there are probably better professional set-ups, but for me it provided a consistent 'check' on what they are getting. You can play with the dimmer or the height to find out what the plants like best, but once you do you can repeat it.