I installed trim tab indicators on our last boat and this one too....it sure is nice to know where your tabs are at, especially if you use your tabs down when in a no wake zone.
My wife learned really quickly to KNOW where your tabs are positioned......we left a no wake zone and she "thought" she had both down, she hammers it to get the boat on plane and the boat pitches hard over to port, I tell (yell) to get off the throttle and reset the tabs....she does that and I say that's why I installed the indicators....look at them before you take off. Now that's just one more thing that's part of the "check list" before taking off. So for us, it's worth the money.
But it's like everything else, whatever it takes to make boating more enjoyable for YOU - whether it's indicators, big stereo, etc......