It's the first time I've used one to be honest bud. It can't be any worst than the other makes I've tried though to be honest. Of them all Interpet Delta Therm tend to fail the fastest, and usually by sticking on.... I have a Fluval E heater that we've had for many many years, but they need quite good circulation to work properly and are seriously ugly. The Rena smart heater I had didn't last 5 minutes before failing on me. A Hydor external one I tried once did ok, but then started leaking...
So, at the moment I have a Delta Therm in my big tank in the living room (basically as I already had it, unused), an Eheim in my 30 litre, a Dennerle Nano ThermoCompact in the 50 litre, an Interpet Nano heater in the Opae tank and that AquaEl Gold in the 60 litre. Surely I'll find at least 1 half decent one amongst that lot eh?
Oh and got 2 Marina 10 watt nano things ordered for the planned nerite rearing tanks too. I'm probably not going to put a heater in the 60 litre retirement/cull tank under the big one to be honest, too much plugged in there already.
The one thing I have noticed though is that the calibration seems a touch out. I set it to 19 degrees but it's maintaining the tank at 22 degrees Celsius. Luckily though that's not a biggy, as 22 degrees is absolutely fine.
I'll get another pic up in a bit bud, finished filling it now and added the marimo balls I'd bought for it a while ago. Also got 20 more ceramic shrimp cubes ordered (quite a lot of which will go into this one) and 3 floating rock island things, my wife spotted on eBay and asked for, ordered but they'll take a while to get here from Hong Kong. The floating island things should add a bit more vertical interest to an otherwise very low down design.