I purchased my 4S in late January of this year.
I could never go back to an Android or Blackberry. The iOS is so easy to use and it's great being able to carry one device for everything.
The thing about Apple is that updated products are constantly being worked on and/or released, so you can bet that your new iPhone/iPad/MacBook/etc. will be considered "outdated" in a few months, or even weeks or days.
That said, I've never had a problem with any of my Apple products. I'm currently using a three year old MacBook and a two year old iPod Classic, and both of them are running as good as if they were brand new.
Needless to say, I'd upgrade to the 4S now.