I have just started using NST recently, and I have to say that I really find it amazing.
It is 100% operational on my "oldie" N95-1 and more efficient that friend iPhone applications !

My suggestions would be :
-> having more translations available (starting from french :) )
-> having it available for all the Nokia plateforms with GPS phones, in order to increase the databasis of users (S60v5, MAEMO, ...)

With the recent launch of the dedicated website, this occurs that this application would grow again and again, so I hope this is just "the beginning".

I go back using it for my running sessions ...