mapnik wird jeden mittwoch gerendert.
osmarender kontinuierlich. (also oft schon nach mehreren stunden).
fuer osmarender kann man auch auf http://informationfreeway.org ein rendering requesten falls man es schneller haben will.

I switched from NoniGPSPlot to OSMTracker. Our area is well covered by sat-images but now with OSMTracker I'm using the GPS again.

yes.
mapnik layer is updated every wednesdays.
osmarender usually within several hours.

tracks are always useful. If you don't have the time to gather tracks and are comfortable lending your GPS, you might want to give it to people that are on the road (driving schools, trucks, taxis, ...).