It has a few great episodes, but for the most part I find its reputation to be well earned. The scripts aren't as tight and the budget just isn't there.
Agreed. Bob Justman said they were almost reduced to doing radio shows due to the impacts of the vastly reduced budget.
Still there were a handful of very good episodes (The Tholien Web, Elaan of Troyus, The Enterprise Incident, Day Of the Dove) and a bunch of stinkers (Spock's Brain, And The Children Shall Lead, Plato's Stepchildren, The Way To Eden). But mostly, the third season episodes were BORING.