I've got Memory Map running on a Dell PDA with Dell branded bluetooth GPS receiver. If I move it when it's switched off (ie transport it in my bag to another part of the world), it sometimes takes up to 15-20 minutes to find it's new position.
Switching it off and back on again at the same location, the sats are found much faster. On the sats page you can see it trying various satellite options when it doesn't know where it is.
The Garmin 430 and 496 in the aircraft are very fast in comparison.