Perhaps wirth differentiating between a panel mount GPS, aviation handheld and the assorted collection of other stuff that people seem to bastardise for the job.
I have never had an IFR panel mount GPS fail in 3000hrs of using them. I have had a panel mount with a weak signal due to an antenna housing that had cracked and allowed water in over time. I have never had a failure on a aviation handheld from hardware problems and have been through 196,296 and now on 496. I have had signal loss on a couple of occasions when using the built in antenna when the panel mount 430 has still been perfect. I have not had a signal loss when the 496 is connected to the external active antenna.
I have had more steam bits of kit fail then I have fingers and toes to count. My ADF is a King ADF and every couple of years loses the plot and has to be reset. Main problems with the DME is moisture creeping into the display and the numbers not displaying. My HSI has failed a couple of times. The GNS430 is connected to both the HSI and a 106A indicator for redundancy. The Garmin indicator has never failed.
I have had numerous AI fail including one on a Seneca where the AP is connected to the AI and we were mid channel IMC and the AI toppled with the AP attempting to follow it.
I have had numerous vac pumps and alternators fail, all usually in IMC! I now have a redundant electric vac pump and NiCad battery pack to drive the avionics.
I would agree, most Narco kit is crap, although I have a couple of perfect examples over time that have been faultless. Alas the minority!