For completeness, one specific case not mentioned is opening a huge file. For each file you open, Sam creates and initializes a temporary file several times larger. If you open a gigabyte-size file, the initialization takes a while. This may have been optimized away in 9front, but I don't know if they ever saw a need to. It's more of an issue in Acme. For instance, working with virtual machine files, I used to accidentally click on ISO or HD images instead of tiny Qemu launcher scripts and Acme would freeze for minutes.