Besides being a little hard to set the temperature, which there are videos of how to do it on youtube, it holds the temperature perfectly. I have a 5.5 gallon tank in my room that is sometimes in the low 60s°F over night. I keep my tank at 80°F. I've never had a single problem with this thermostat. I never even see the tank temperature off by 1°F.Yes, its a little large, for its wattage, and also for my tank size, so I have it installed on an angle. Its probably large for a reason though, so I am fine with that.The suction cups aren't the greatest, they still hold but after weekly cleanings for the past year, where I do take the thermostat out, the suction cups are getting weak. You can buy replacements EHEIM Jager Double Suction Cup Holder or lay the heater on the floor since it is completely submersible. I am planning on replacing the suction cups with magnets anyway, but sometime when I have more time to play, but I do think the suction cups will hold until I am ready, and that may be awhile. The power cord is great, it is long, has a great feel, and I don't think I will ever have a problem with it.The main reason I chose this was one review I read. Their tank leaked while they were out, losing all of the water (poor fishes), and this heater suffered no harm from that.The price is great too, for such a quality product, its priced the same as the junk ones in the chain pet stores. That one couldn't even keep the temperature consistent, let alone heat up the tank to the temperature I wanted. It was also a 50 watt heater like this one too. This one doesn't spend a lot of time on unless I just changed the tank water and its bringing everything up to temperature.If all Eheim products are like this, I would use all of them.