I agree with jpines... I love mine. BUT... It's definitely NOT required.
I really like the fact that I have just as much control over my powerheads as I do my lighting. (The Radion lights do have minor control over your Vorteches... But you have the ability to fine tune them with the ReefLink.) I'm also looking forward to getting the camera that is supported by ReefLink.
My decision was made by not having the money to buy the Apex controller I wanted. It was a quick way to curb the desire to have certain features I wanted without having to drop all that cash.
However, after setting it up and really getting into the features... My favorite feature of the ReefLink is that I can control it from my iPhone and iPad. I hated having to pull out my computer and connect it to my lights to adjust things. (In my opinion, changing the schedules and settings is easiest on the iPhone. Even easier than Ecotech Live.)