I have also noticed real troubles with Drive and PR1.3, but OTOH there were days when it really sucked with PR1.2 too. Not sure if it's 1.3-related or not, but I also last Saturday got an instruction to 'turn sharp left', when the arrow and actual road was turning right (and then spinning round towards the left).

I think that in general the GPS antenna is probably not sensitive enough, and the Drive app's internal logic is bad:

If I have been sitting happily on a road for the past 30 seconds, driving at reasonable pace, it is a good assumption that I am still on that road, instead of suddenly on some side road. Drive does not appear to make this assumption and will have me suddenly jumping all round the place if there is any level of cloud cover and other roads nearby.

I hate to say it, but if I want reliable GPS then CoPilot on the iPhone has proven to be a better (albeit not free) solution. In Nokia Drive's defense, zooming around in it is much faster, and you get 3D buildings.