We have two extra freezers in our basement. One typical $150 chest freezer from Lowe's, the other a commercial stand-up type.
There are advantages and disadvantages to both.
The chest freezer holds cold air better. When you open the door, the air doesn't "fall out" like it does in the stand-up, so it doesnt take as long to re-cool the air once you open it. More efficient.
But the chest freezer is hard to organize. You forget about food on the bottom. You go digging around and you wind up messing up any organization you have. We've tried bins, everything, and its just tough to organize the contents in a good way.
What we've come up with is using the stand-up freezer for meats. One shelf for each type: beef, chicken, pork, seafood. Loaves of bread go in the door trays. We're about to use bins in each shelf b/c the steaks and stuff aren't stacking well, and slide around and fall when we try to get something out.
The chest freezer gets vegetables, ice creams, frozen dinners, any overflow from the upstairs "normal" freezer.
I use a shot glass with water frozen in it, with a quarter set on top so that I can tell if the temps get high while I'm gone, then refreeze.