Wireless ethernet (IEEE 802.11b, sometimes called WiFi is the most popular) is becoming very popular but it seems few people understand that they are essentially opening up their own personal and corporate information to outsiders if care isn't taken in the implementation.
My university has an 802.11b network for students to access the internet on campus and last term I had a coruse in wireless networking - an extremely interesting topic.
WEP is quite simply a joke, a guy with a laptop, wireless card and a big RF antenna can sit up to 300 feet in his car and break the 40-bit encryption in less than an hour. All he has to go is guess the network name, which is usually pretty easy. Until wireless security gets better, use a VPN - you might regret it if you don't.
But if you don't care about privacy of data, it is a great improvement in convenience over wired if you are using internet access...but even 802.11a (54mbps) is kind of slow for setting up a serious corporate network. Remember that the network can only use about 60% of its bandwidth for data transmission - so your supposed 11mbps 802.11b card will probably get around 6.5mbps under ideal conditions, 802.11a will get around 30mbps at close range.