Yeah I've gotta say I wasn't sure about the strength or longevity when I first started printing parts about a year ago now. I tried Stereo litho printing with resin, the detail was excellent but the parts were a bit brittle.
The laser sintered nylon parts though I've been totally amazed at - really strong.
In fact I had a spare connecting part the other day - it was a 2mm diameter rod that was about 6 inches long - I can bend it all the way round in half and it still doesn't snap.
I wasn't sure if the 'hook' part was going to be strong enough when I designed it so I over engineered it to make sure. It's an oval shape that has a slight twist to it through it's length - the oval is 12mm by 15mm and I sort of modelled it on a human femur bone.
I'm totally confident on the strength now - I reckon I could bolt it to a tree and hang off it now.
I think the home filament printers (ABS/PLA) will improve in leaps and bounds in the future.. and hopefully when that day comes I'll already have a big catalogue of custom parts that people can just print for themselves on their home printer.