I should add "YET!". Apple made available firmware 2.0.1 for the iPhone and iPod Touch.
If you have an iPhone 3G (non-jailbroken), original iPhone (non-jailbroken and locked) or a pristine iPod Touch, then you should definitely upgrade to this latest firmware. So far all reports show that applications runs faster, quicker synchronization with iTunes and spiffier overall functions of the iPhone or iPod Touch.
WARNING: if you are not in the above group of Apple device owners, meaning you have jailbroken and/or unlocked your iPhone or iPod Touch you should NOT upgrade. You will need to wait for the hacking community to update their hacking methods (currently Pwnage Tool) before doing any firmware update.
The only exception will be the iPod Touch owners who had jailbroken their device and do not mind returning their iPod to Apple factory condition (ie. no more unauthorized 3rd party applications).
BTW: As I have reported on Twitter and other Social Networks, I am experimenting with a method to resolve much of the frequent crashes on the iPhone with firmware 2.0. I will be reporting here on my blog as soon as I have definite results. Please stay tune.