When debugging or test web applications it can be useful to increase latency or decrease bandwidth to see how your application works with poor network connections. The modem simulation rule option will do this for bandwidth but latency is more difficult to accomplish using this rule. Having the possibility to do this in a more controlled manner would be really helpful. We now have to resort to multiple tools
You can add a simple *delay rule in Fiddler's AutoResponder list to delay outbound requests by a fixed amount of latency.
Full traffic shaping is actually an extremely complicated problem, and really needs to be done at the network adapter level for full fidelity. You could use something like Clumsy for this.