Remember that by default, every time you edit a resource, the entire resource cache is cleared and the next visitor to every page has to wait -- and the difference in whether the user leaves the site because page-loads are too slow is measured in milliseconds.
I'm not sure if tags in the template are cached or not. You can look in the core/cache directory to see if you can find the processed versions of your output modifiers.
That's a good point.
I had a look at the cache directory, it appears that conditional output modifiers are NOT cached and have to be executed each time the page is viewed which will certainly impact performance. Normal output modifiers are cached.
Chunks are not cached separately, they appear to be cached within each resource-cache. I was under the impression that they are cached separately (for redundancies sake, considering the same chunk may be invoked by many resources in the same way, so why not allow them all to draw upon that cache, instead of caching it individually..)
Thanks for all the input folks
