I used my oven for the first few batches of jerky, before I was willing to commit to the cost of one of the home dehydrators. My oven's temp wouldn't go low enough for my liking (170 is the lowest setting), so I propped a wooden spoon in the door. Overall it worked just fine. I think I did 4 batches before I bought a dehydrator. Downsides to using an oven:
1) it takes longer. I think it takes me about 4 hours to do a batch of jerky in the dehydrator (depending on thickness), and it took me 6-8 hours in the oven.
2) it's A TON messier and more difficult to clean. I had to scrub the wire racks before and after a batch of jerky (and those things aren't the easiest to really scrub). Then scrub the bottom/sides of the oven before, place tin foil down, then scrub the sides after. Even at that, I usually missed something, and the next time the wife used the oven there was smoke everywhere. With the dehydrator, I just throw the meat on the racks and when its done I toss it in the dishwasher. Done.
Both return a quality product though. I like my jerky a little on the chewy side though, so a quicker finish works better for me. YMMV.