I have had the Netgear DG834G for quite a while now connected to a Windows PC through Ethernet cable and wirelessly to a Apple Powerbook without any problems.
The DG834GT has a 108mbs speed verus 54mbs on teh DG834G. You will not see any difference in internet speed usinng any of the two. If you are sharing files across a small network, then the DG834GT has a maximum speed of 108Mbs. However to get the maximum transfer speeds, you would need to also upgrade the wireless network cards to the netgear 108mbs speed.
If you are connecting via LAN/Etherenet, stick with the DG834G