I'm having increasing problems with poor network performance at public wi-fi hotspots.
I'm particularly susceptible to bandwidth problems, because I do a lot of interactive work on the net. Most people use the net in batch mode: fetch a web page, download an email, and the like. I'm often logged into a remote server, transmitting small packets of information a keystroke at a time.
I have a sneaking suspicion that a lot of times I observe network performance problems, that's because somebody is being a bandwidth hog. They may be doing something like connecting to a streaming music server, which uses a continual and significant part of the network bandwidth.
I have no hard data to support or disprove my theory. So, this afternoon, I did a little research. What I want is a network analysis tool that puts my wireless interface into promiscuous mode (that's a mode where an application can see what everybody is doing on the network), and then accumulates network usage by the various devices on the net.