Pros: dead sexy, easy to use
Cons: mail client, slow, no GPS
I'm going to focus on the bad. There are tons of iPhone reviews out there where the fanboy who bought it, tries to verbally hump it in his/her review.
The basic rules of thumb for the G1 iPhone are as follows:
1) If you love to email on your blackberry, wait for the G2. The G1 mail client is for children.
2) If you want to be able to navigate to/from someplace using your phone, wait for the G2. The G1's triangulation feature is no substitute for real GPS.
3) If epically slow data transfer (read: web browser) really bother you, wait for the G2. G1 is slower than death.
So basically wait for the G2 iPhone unless you want to save money by buying a used G1 and dont care about the items on the list above.