I'm currently using a Hovobator (the styrofoam ones) - they're fairly inexpensive, but the temperature control is crude. You just turn a knob to "increase" or "decrease" temps so you'll need to monitor for a while with a thermometer (doesn't come with one) before adding eggs to make sure you are at the right temp (mine was steady for a few hours and then about 12 hours later was about 5 degrees more than I wanted). And when it does maintain the temps you want, it's not completely steady. Depending on outside temps of the room it's in it will fluctuate within about a 4 degree range from what I've seen so far. That kind of change isn't a big deal for me but if you have eggs needing more control you may need a better incubator.
This is not necessarily a product endorsement, just a review so you can make an educated decision about your purchase.