Its great for workflows involving using the same programs frequently where it will then then go ahead and preload it in memory for you to make subsequent starts faster. This will cause the RAM to be used up with programs that it predicts are frequently used and will delay the startup of rarely used programs as the pages need to be evicted to make way.
For the Whonix usecase where we have transient setups because of snapshot rollback or DisposableVMs, its presence would be of almost no use(?)
Here’s a review with preload benchmarking and system responsiveness comments. It seems good to have.
https://www.hecticgeek.com/2013/05/using-preload-ubuntu-13-04/