Version:           0.9.svn1028043 (using KDE 4.3.1)
OS:                Linux
Installed from:    SuSE RPMs

I created a GSM 3G connection in KDE 4.3.1's knetworkmanager, and tried to set the network type to "Prefer 3G", but knetworkmanager - unlike Gnome's nm-applet - ALWAYS forgets this setting. Neither reminds it the setting nor sends it to NetworkManager. Let's compare the dbus data of KDE and Gnome created connections. Both connection entries were created as default, I only changed the connection name, the APN, the PIN code and the network type (which has no effect in KDE). In knetworkmanager, I also had to fill in the Number, because it has nothing as default instead of *99#, like Gnome's nm-applet.

KDE 4.3.1's knetworkmanager:

[Argument: a{sa{sv}}
{
   "connection" = [Argument: a{sv}
   {
      "autoconnect" = [Variant(bool): false],
      "id" = [Variant(QString): "T-Mobile H"],
      "timestamp" = [Variant(uint): 1254892750],
      "type" = [Variant(QString): "gsm"],
      "uuid" = [Variant(QString): "6910b46d-f510-44d6-84bf-dd24269cb425"]
   }],
   "gsm" = [Argument: a{sv}
   {
      "apn" = [Variant(QString): "internet"],
      "number" = [Variant(QString): "*99#"]
   }],
   "ppp" = [Argument: a{sv}
   {
      "baud" = [Variant(uint): 0],
      "crtscts" = [Variant(bool): false],
      "lcp-echo-failure" = [Variant(uint): 0],
      "lcp-echo-interval" = [Variant(uint): 0],
      "mppe-stateful" = [Variant(bool): false],
      "mru" = [Variant(uint): 0],
      "mtu" = [Variant(uint): 0],
      "no-vj-comp" = [Variant(bool): false],
      "noauth" = [Variant(bool): false],
      "nobsdcomp" = [Variant(bool): false],
      "nodeflate" = [Variant(bool): false],
      "refuse-chap" = [Variant(bool): false],
      "refuse-eap" = [Variant(bool): false],
      "refuse-mschap" = [Variant(bool): false],
      "refuse-mschapv2" = [Variant(bool): false],
      "refuse-pap" = [Variant(bool): false],
      "require-mppe" = [Variant(bool): false],
      "require-mppe-128" = [Variant(bool): false]
   }],
   "serial" = [Argument: a{sv}
   {
      "baud" = [Variant(uint): 0],
      "bits" = [Variant(uint): 0],
      "parity" = [Variant(QString): ""],
      "send-delay" = [Variant(qulonglong): 0],
      "stopbits" = [Variant(uint): 0]
   }]
}]

#####################################################

Gnome's nm-applet:
[Argument: a{sa{sv}}
{
   "gsm" = [Argument: a{sv}
   {
      "band" = [Variant(int): 0],
      "network-type" = [Variant(int): 2],
      "number" = [Variant(QString): "*99#"],
      "apn" = [Variant(QString): "internet"]
   }],
   "ppp" = [Argument: a{sv} {}],
   "serial" = [Argument: a{sv}
   {
      "baud" = [Variant(uint): 115200]
   }],
   "connection" = [Argument: a{sv}
   {
      "id" = [Variant(QString): "T-Mobile H"],
      "timestamp" = [Variant(qulonglong): 1254871464],
      "uuid" = [Variant(QString): "4138751a-8a85-40b3-b5ff-8dcad7430cad"],
      "type" = [Variant(QString): "gsm"]
   }]
}]



You can see, that knetwormanager created tons of PPP and serial data despite leaving everything unchanged as default, but in the gsm section it lacks "band" and mainly "network-type" atributes.