Charles is awesome. We used it to debug connectivity with some third-party web service over HTTPS -- absolutely worth its money.

Absolutely. Charles can sniff SSL by acting as a man-in-the-middle Certificate Authority. Very clever!

Looks good. I'll give it a try, thanks.

One problem I have is dealing with viewing my Comet connection (long-lived XHR). I stream JSON to the browser and Fiddler picks up and is able to display all this data, but prevents it from being received by the browser. Would be nice to not have this problem so I can see my JSON events in Fiddler and in my UI.

Have you tried tcpTrace (http://www.pocketsoap.com/tcptrace/)? It's dead simple, so I wonder if that may help. I haven't ever used it with long-lived XHR, so I can't say it'll work, but it's a free, 224 KB standalone, so it can't hurt to try.

Can you let us know if you had better luck with Charles?

Sure thing.