802.11g has a theoretical speed of 54Mbs, well in excess of your Internet speed. You wont reach that speed in practice.
The 802.11n system is arriving on the market, but personally, I would keep clear for the moment. The system specification has still not been finalised by the IEEE and therefore, various components (especially from different manufacturers) may not work together at all. All manufacturers offering this system will refer to it as "draft".
Where wireless will be slower than a wired connection, is for large file transfers - graphics files for example, from computer to computer. But for Internet access, you wont perceive any difference.