Nimbostratus
Nimbostratus
No, I do not believe that there are any hard limit values to the number of iRules that can be applied to a Virtual Server. The general answer is "how many can you add before the logic degrades the performance beyond what you are willing to tolerate."
To answer your second question, there is no limit to re-directions either. You can measure the performance of your iRule using Statistics and the timing command (http://devcentral.f5.com/wiki/iRules.timing.ashx).
The reason that there are no limits posted is because the usage of the BIG-IP varies from customer to customer (the modules installed on each device, the configured usage of each module, the level of traffic / TPS that a box must sustain, etc.), so they have given us the tools to measure the performance impacts ourselves (you can measure the performance of an iRule or even portions of an iRule).