The LGNPC project does not address the cliff racer harassment issue nor does it affect the frequency of idle greetings from NPCs. If those are of paramount concern then it is pretty difficult to justify using LGNPC mods.
It is impossible to decide for another player if it is worthwhile to include LGNPC mods in their game. Some players interact sparingly with NPCs - only speaking with them to get quest-related information or directions to a person or location in a town (information that most experience players already know). For such players, there is little value in using LGNPC mods. In a LGNPC town, different NPCs have a unique response on local topics such as 'services' and 'someone in particular', but it is essentially the same information that Bethesda provided. It is true that most LGNPC mods add some new quests to explore, but some players might find it tedious searching different dialogue topics in the hope of stumbling into a quest to perform - particularly when the majority of NPCs won't have a quest to offer.
Because of the scope of the project, mod conflicts may be a real concern. Happily, the dialogue-only versions of LGNPC mods virtually eliminate that risk, but at the expense of offering any quests. Once again, we return to the question "is it worth it?"
I suspect most users of LGNPC mods just have them simmering in the background on the off-chance that they might like to learn more about an NPC. Ever wonder how Fargoth and Arrille came to be friends, how the outlander Neminda came to hold such a position of responsibility in House Redoran, or why Jobasha came to settle in Vvardenfell? Those stories are a reward to players who value such things. Is it immersion-breaking to visit a non-LGNPC town? Maybe, but perhaps no more than playing Morrowind without LGNPC mods since each NPC in a town has the same response on several local topics.