2.4 mgz devices may cause problems with a wireless system. I have used a 2.4 cordless phone while sitting at and using the laptop, with no signal change. In addition, my home is controlled by X-10 devices, and so far no problems of any kind.
Wireless 2.4 mgz cameras have had no impact on the lan system. However the router has a big impact on the wireless camera operation, to the point of making some of them blank out from interference. In fact, I had to shut down the wireless router in order to use wireless cameras. (In like fashion, using the 2.4 mgz cordless phone would blank out two of the cameras as well.)
This means you should be prudent in your use of products and their locations as each of the devices are competing for space in the same 2.4 mgz frequency channels. If you are just starting out it would be beneficial to have some of your devices in the new 5.8 band.
I have tried several driver and firmware upgrades for the DWL-G650 card. Each version gives different readings for the strength of the connection, and at times the quality. The built in XP program that gives the same information has always given the same readings. This leads me to believe that the D-Link program may not be accurate.
Average connection through the wired ports and wireless: I get an average of 108 mbps. Figures don't mean much to me, so in actual use, the speed of the internet is just as fast either way. The speed of file transfers for small to medium size files is nearly the same.