I'm very excited about my new food dehydrator! We got the Excalibur 3900 Deluxe -- it is a very serious food dehydrator! I took a class at our local state cooperative extension and got all revved up to experiment with drying foods. The benefit of dehydrating food over freezing is that no energy is needed for long-term food preservation, so you don't have to worry about losing your food due to a black-out or freezer failure. Since our freezer stopped working back in July and I almost lost everything in it (a fully-stocked, large capacity, full-size freezer), I can definitely relate to how devastating that could be. I spent a while researching types and models and finally decided on this one.
I'm no expert, but here's what I learned in my research. There are two basic types of dehydrators: those that dry back-to-front, and those that dry from bottom-to-top. The bottom-to-top types are usually circular and have donut-shaped trays with a hole in the center. Because the blower is located at the bottom of the unit, the bottom trays dry first so you have to rotate the trays around to ensure even drying. These units are fairly inexpensive.
The back-to-front units have the heater/blower located in the back, so the air blows evenly across all of the trays. Also, these units don't require a hole in the tray so it makes it easier to arrange the food. This comes in handy if you want to make fruit leathers (basically it's a fruit roll-up, without all the added junky ingredients!).
I have found the Excalibur 3900 to be great so far. It has 9 trays. They also make a model called the 3500 with only 5 trays, which might have been a better choice for the majority of my drying needs. The 3900 uses more electricity so if it is not full, you aren't getting the full benefit. However, it was completely full when we made venison jerky so the 9 trays came in very handy that day.
So far, I've made "sun-dried" tomatoes and venison jerky. I plan to make dried apple rings very soon as a very tasty and healthy snack for my kids. I am also psyched to make some fruit leathers ... my older kids will be very excited about these!