Is there a major benefit in speed or other benefit if you use a spritesheet over just separate images of the sprites (EG: player sprites, terrain sprite, etc all in different files)?
In one of my former projects I used individual images. I can tell that if you want to copy like 1000 small PNGs to an USB stick, it takes like, ages. Loading is still fairly fast though.
I assume with a harddisk you don't notice this.
I then switched to zip archives containing all the small images. Makes it easier to handle, but harder to access. It allows to bundle meta data with the images though, and keeps it all together. This is a benefiot that I started to like.
It also becomes increasingly difficult to name the files, if you have them all in one folder. If you have 0000.png ... 1752.png it will become reall hard to find something.
Sprite sheets circumvent some of these problems. But if you have sprites of vastly different sizes, sheets with a fixed raster become inefficient, and you must looks for better organization of the sprites on the sheet.
I've been using both, and still couldn't make up my mind. It's not too hard to change even late in a project, though, so it wasn't a big issue for me so far.