Phone is a Samsung D600, it only has GPRS.
The N70 has GPRS, EDGE and 3G, not sure about the N71. My friend is happy with his N70. To keep his phone on 3G, he keeps it vertically placed on his desk. If your 3G signal is strong where you live, the phone should stay on 3G.
I must add the netmonitor is a bit of a geeky menu to operate on the 6680, so maybe you'd rather not go that route.
What model of Samsung is it? It may be that it only has GPRS so at about 40kbps it would take at least a minute to download the 500 kByte required for the speed test.
I used it under Linux or XP. Same issues.