They can work beautifully. BUT you have to be patient and willing to take your time to really figure out what works best for you.
I tried to get fancy with my first one and it was more trouble than it was worth even though I had a few great hatches with it. Below is my current one. It is an older end table can get with a glass front. I have a small desk fan in the bottom and I heat it with 5 (small) light bulbs.
Most people would say that is crazy but it works great for THIS incubator. Plus if one goes out I have no major temperature dips. there is 1- 40 watt, 1-7.5 watt, 2-15watt and one 40 watt LED which produces almost no heat but gives just enough to bump the temp to 100F. It took almost a week to figure out which combination worked best. I used to use just a single bulb but after losing a hatch when it burnt out (it was brand new too) I decided having multiple bulbs was better for me.