Seriously I do not see any value in knowing the speed of fellow Wazers. That is raw data; I have Waze turn that into routing advice that helps. I do not want to/can do all the computations myself and I trust that computers are more fit for that.
How much delay will trigger a trafficreport depends on the segment(s) you are driving and how much historical data is available for that segment. Very short segments may not report traffic.
Once traffic is reported it propagates to wazers concerned within seconds - less than a minute by all accounts.
And what exactly do you want to compare with what? MapQuest and Google get their trafficdata from undisclosed sources. They both miss the granularity that Waze has (provided there are enough Wazers in an area) and only signal traffic on the big arteries and freeways.
AM for some 25.000 km² around Maastricht, the Netherlands
iPhone 3Gs / iOS 6.0.1