I think Firebug gives me more accurate info regarding object fetch time.
For example, this URL, http://platform.twitter.com/widgets.js, overall taken 1.43s to load.
According to Firefox’s developer tool, 914ms of that is for “connecting….”.
Firebug however tell me that overall it tooks 1.41s to load the object and of those 914ms is in blocking state.
If multiple requests are to be sent to the same server IP, they are queuing up and time spent in queue is “blocking” time.
Without this clarification, one could wrongly interpret “Connecting…” time as the time taken purely for 3-way handshaking.