What i do to make it work great is imagine the GPS to be a mirror, and i want it to reflect the sky. So i give it an angle such as the white of the PSP290 sees most of the sky.
Sometimes it takes time to get the signal (when the sky is clouded it can take 2,3 minutes), but it works.
Before, i was using the GPS fully deployed (near vertical, the white facing me) and it was always loosing signal.
It works great in my car, but i have a convertible.
My only concern is that MapThis crashes often. Sometimes i cannot even load the maps, sometimes it is when i zoom ... but i see nothing wrong in the source code, so i don't understand.