I didn't bother to read five pages of squabbling and troll-feeding.
My 4S has shown near identical performance to my 4, which was only 8 months old when I upgraded. Similar battery drain, and I can still go a couple days without charging.
To have Siri, a dual core processor that's noticeably faster, and a camera that will blow most point and shoots out of the water? Yeah. I'd say it was totally worth the upgrade.
Not only that, but no one's commenting on the much, much better service from the redesigned antenna. I live in a remote area, and while my 4 would drop calls frequently, or I'd have to repeat things due to a bad connection, that's not the case with the 4S. I've yet to have a single dropped call, and I haven't had to repeat anything, as my voice comes through clear.