That depends entirely on what you call minor. A lot of people on HN think that it's absolutely essential that a page loads and responds within a few milliseconds, because somehow subconsciously to users, it will make the site feel snappier, and thus better, and thus more worth paying for / sticking around on.

Compiling and running LESS on the fly in production might, besides the extended load time, increase the chances for a flash of unstyled content. If this makes you nervous, don't run LESS on the fly in production.