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From every review and user testemonial I've seen here in Sweden, both GPS and WiFi are reported to work perfectly.
Are you sure that your users are using VoIP all the time? Wifi connects here too, there is no problem there. BUT, it disconnects out of the blue every 30-40 minutes. And if at some point try to browse something, chances are that it will again disconnect out of the blue too and it will need to reconnect. I even went as close as 2 meters from the router, but the problem remains. My E61 and N80 do NOT have this problem on the SAME network.
As for the GPS problem, check the link I gave earlier. There are many people where lock-in takes impossible time to complete. For me, it never did.