My experience has been quite different recently. Upon opening unav, I
have a reasonable position in a couple of seconds, and seem to have an
accurate GPS position within around 10 seconds.
In most cases, the route is found in a couple of seconds. I've had it
get stuck on searching for a route a few times, though most times this
is when there is no network connection, something unav should probably
detect and give some better feedback on.
Last week, I actually used this alongside my friend who was using
Google Maps on a Nexus 6P, and I was getting a faster and more reliable
location detection (using unav on Nexus 4). The Nexus 6P also had a
network connection, while my Nexus 4 was offline (my friend was
roaming, I was not).
So, overall, the location detection is brilliant in my experience over
the last couple of months. Unav is also quite nice, but could still do
with a few small improvements to improve it's reliability.