SmallNetBuilder's NeedToKnow articles are one of the best intro tutorial to WiFi. The Wireless Networking NTK - Introduction has this bit about Wireless Networking :

"But before we start, here are our three rules of Wireless Networking:

It never goes as fast as they say it does
It never goes as far as they say it does
It never sets up as easily as they say it does
Still interested? Good! Because the Three Rules aren't intended to discourage you, but more to prepare you for a successful and satisfying wireless networking adventure. Let's dig into each of the Rules and see what's behind them."

One of the articles deal with Wireless LAN Performance Improvement.

I would strongly recommend anyone who is thinking about going WiFi read the articles on SmallNetBuilder.