I use both BT and wifi.
Wifi at home and at work to connect to my networks and internet.
BT I use to connect to internet with my old bt cellphone when I dont have access to wifi.
I use bt with my gps. In car with SmartST voice navigation program together with my bt-headdset I can easy hear all voice commands from SmartST.
I also use bt with my nokia 6310 bt cellphone. Together with Running Voice GSM om my ipaq it gives me a solution that is as near as you can come a pocket phone without buing one. My old nokia 6310 works like a very intelligent bt headset together with rvsgsm on my ipaq.
The best of all is that I can use all above bt connections at the same time
I have an ipaq 5550, an ericsson bt headset, a nokia 6310 cellphone with wired headset and a navman 4400 bt gps.