How many apps until performance is affected?

[rdstoll]

Hello - I am coming from the smartphone world where you had to be extremely careful with the number of applications/add-ons you could put on the device before performance was negatively affected. Obviously, the 3G iPhone has a helluva lot more horsepower and storage to deal with this, but I'm wondering whether or not installing a bunch of apps will eventually lead to spottier device performance. And while I'm at it, is there an iPhone equivalent to the "Task Manager" on Windows Mobile devices?

Thanks and love the phone!