I am using it with the Garmin IQue 3600 PDA with built in GPS navigation system.
The card is certainly reliable and the speed is OK. I haven't tried any other card so I can't say exactly how good the speed is compared to others. It does take a while (a few minutes) to load heavy map files (more than a 100MB) from the computer to the card using the PDA. But it works fine when using it in the PDA for in car navigation (when it reads maps from the card and displays on screen ) and for playing and recording Audio. So I have no regrets about buying this