On the iPad, if by rumble you mean some sort of audible feedback when you touch a key, you can turn that on and off in settings:general:sounds: keyboard clicks.I like iPad Safari for viewing the forums. On my Blackberry it is definitely a last resort. The screen is just to tiny for me and the controls to zoom in and out are too much work now that I've had a taste of the Apple mobile browser. My next phone will probably be an iPhone.
The rumble is probably available on an iphone or ipad with 3g. It's the motor vibration if you set your phone to vibration mode.