UPDATE : while the Antenna fix helps, I ended up RMA'ing the phone back to LG - the new phone is now out performing my old Nexus4. So I now conclude that the only REAL fix for a poor GPS is a new phone....
Both my wife and I have Nexus 5s and both have the same terrible GPS performance so I was convinced it was inherent to the phone but the rest of the internet was silent on the issue. It wasn't until digging through the XDA Developer forums did I stumble upon a post that gave me some hope. Apparently there is a fit up issue between the back cover that contains the GPS antenna and its spring loaded connector on the main board. That was all the excuse needed to break out the case cracking tools give this potential fix a try - and I'm glad I did - while I haven't performed any extensive field test my initial post fix comparison in the video above do indicate a positive affect.
