You won't experience any lag becase of the wireless configuration, the bottleneck occurs with the internet connection itself. Even if you have a cable broadband connectioin that runs at 6 mbps, it won't lag because at the bare minimum 802.11b has a throughput of 11mbps and 802.11g is at 54mbps.
If you want to transer large files from two computers, you WILL see a difference because typical wired networks work at 100mbps twice the speed of an 802.11g network.
But your question was internet related... and the answer is NO your internet will not lag because of your wireless connection. (Take it from me, I'm posting this using my laptop, DSL, and a 802.11g connection... no problems here)