If anyone is interested, n900 Texas Instruments NaviLink 5.0 (NL5350) is know to be inferior to Sifrstar III chip (common for WM devices).
The TI chip lacks sensitivity and needs more time to acquire position.
Yeah, that's another Nokia's cheap economy, together with scratchy touchscreen and tiny battery.

The iPhone chip is Broadcom(?), which is even less sensitive, given the tiniest antenna in GPS history - the camera metal ring! So Maps.app power depends on network positioning.

I tested Sygic navigation on n900 today with all networks disabled.
It works. The best way to hold your device seems to be landscape, at 45 degree angle to the ground (like you normally hold a book). A lot of of sattelites popped out in view as soon as I put the device like that. It took about a minute to fix.

With network navigation enabled (I was in the range of my home Wifi), positioning was blazing fast, almost instant - 5-10 seconds.

But still, Sirfstar gadgets - all those HTC, Eten, Asus,Toshiba - owned a bunch of them (8 models in total) - had no problems with device position and were less sensitive to windshield material, for instance. But WM - that's dreadful...