Maybe the question should be "when should I let my media be imported automatically and when should I just click the button?".
I personally never have anything running like autotagging or auto cover art which significantly adds the time to complete an import. More times than not the meta data is not good enough and I have to manually tweek it anyways. I never do audio or video sound analysis during import -- very time and resource hungry, I do it later using a simple smartlist.
If people are recording tv programs while they are at work for 8 hours that of course is something else again. Otherwise, any time I rip or add media to my watched folders, I do a manual autoimport -- its fast. Any time I spend a lot of time retagging from a client, I manualy sync AND run autoimport too. No big deal. And you can listen or watch whatever right away. The import a particular folder option does no reindexing, no fixes for external changes that syncing might have missed, no removing dead links - so I never use that.
However I realize there are a lot of people who just want everything automated and are not so picky with there artwork or genres, so they are given those options.
In the past, I had this set to off, and would only do this manually. Now it works quite well IMHO with little system overhead or network drain.
-- 5 new posts before I finished so a PS fro Matt and Hendrik
As long as I an get it to work like it does now that ok; but not every x hours. I also didn't realise it starts silently on each launch.
BUT, what is so bad about just clicking the import button (put in in the main menu bar even like TA0 said) - never did understand why people want this so badly except for recording TV in one's absence (or making it easier for "torrenting" people out there^^).
That being said, would it be a good idea to separate "folder watching" and the autoimport process? For people moving around files externally or doing admin remotely, I can see where that would be a good thing to have on full auto, but not necessarily the complete import process.