I found out that my Holux M1000 is quite unusable for voice navigation because the fixes from the device come 1-2 seconds too late (it is very weird but that is what I am seeing with the Holux). This also means that I easily miss turns when driving. The cold start speed, sensitivity and battery lifetime are very good with holux m1000.

I also have Nokia LD-3W, LD-4W and N810 internal GPS, and they work much better in this context and fixes come accurately in time when doing voice navigation.
The cold start time of internal N810 GPS could be better but after I have the fix, then it works ok.