I have that one. I got it at Tractor Supply about a month ago and it's been going ever since. I used it as a hatcher successful. My first batch done exclusively in this incubator is going into lockdown today. It was a staggered hatch and I have more due Monday.
Overall I think it's a nice unit. It takes some tinkering to get the temperature adjusted and maintained. Plan on at least 48 hours. The temperature reader it comes with has a plastic card attached. This must float above the eggs. If it drops down in between the turner spaces it'll think it's too cold and raise the temperature. This temperature spike can and will cause spikes. It's also preventable. I use 2 additional thermometers. It takes some practice to close the machine and keep it where it needs to be. Not difficult but something you'll want to be aware of. You may need to adjust the temperature again when the eggs going and turner is on. Place it in a room with the most stable temperature. That'll give you the best success with any incubator.
There is a lot of human error that goes into incubating. Learn everthing you can about temperature and humidity. Not just what they need to be set to be why they are important because of how they effect the egg development. Other things to learn about are candling, turning, weighing eggs, air cells, and more. The 4250 is a nice little maching but cannot overcome human error in these areas. It's not a set it and forget it type machine.