I've had massive issues with Ubuntu on a HDD. Every time a big file was added to disk (like a download), the indexing system would run and render the whole system unusable for minutes (100% disk and CPU). Upgrading to an SSD solved the issue.
That depends how good Linux's support for very-low-priority background tasks is.
UNIX priorities don't handle this situation well because a low priority process is still technically immediately runnable and can cause priority inversions by clearing out all kinds of system caches that your foreground app was using.
