So, you've had semi-negative experience with a different (unnamed) chipset, and read good things about the SiRF Star III. That strikes me as insufficient reason to advise people that it's the ONLY choice.

I have no direct experience with the SiRF Star III. Although it's the reference point for a lot of comparisons, online reviewers have found the MTK chip very competitive in performance metrics, possibly superior on multipath rejection, and a clear winner on power consumption. That could be the tie-breaker for a lot of buyers.

Probably the best known example is the i-Blue 737 (second generation), which has received positive reviews here and around the net. Looking further, the Qstarz BT-Q810 appears to be its twin, right down to the case, with identical specs.

Qstarz bumps it up another level with the BT-Q818, using a higher capacity battery and additional tweaks to extend run time. They also updated the case without changing its dimensions (72.2 x 46.5 x 20mm) or weight (64.7g w/battery).

I bought the BT-Q818 for $70. It works indoors. It works in the basement. It works downtown (Boston, I can't speak for Manhattan). It works behind tinted glass. Importantly, it works out of sight in the bin under my car's center armrest. It goes to sleep when I take my N800 out of range and wakes up when I bring it back.

Qstarz claims 32 hours of active use on a single charge, which seems credible so far. (I was well past 24 continuous hours when I needed to reboot my N800 for an unrelated reason and aborted the test.) Tracking in Maemo Mapper is spookily accurate. I'm very satisfied.