You can do loads with it, practically anything really. Basically it's a packet sniffer/decoder on steroids. You can take a packet trace then the built-in expert system will flag up every 'error' in the buffer, tell you what they are and even give hints on fixing them. Plus it has loads of decodes so you can see what's going on in your Oracle exchanges, SQL, AD, whatever. It has specialist facilities for doing a VOIP analysis including giving you all the call stats, the quality scores, the codec used and you can even reassemble and replay any call. Same sort of thing for HTTP, including being able to regenerate the page the person downloaded and view it - great for investigations into nefarious browsings on the corporate internet connection. You can do a timeline, show where the delays were in a packet exchange, do a 'what if' by changing the number of connections or users to see what would have happened. For wireless it can do site surveys, access point detection and stats and packet capture off the wireless card. It has tools for all the basic Ethernet stuff like utilization, collisions, top talkers, matrix etc. It supports remote probes and will also get data from SNMP or RMON devices and graph them for you.
The downside, of course, is that it costs a lot of money; but if you're going to pay for a commercial sniffer/analyser product anyway then it's certainly worth a look. You can get a demo version off their website that you can play with if you want