With the iPhone OS 3.0 Preview coming this Tuesday, March 17, the question will inevitably become: when's it shipping?!

However, Erica Sadun over at Ars Technica, in an article designed to help developers better target their firmware requirements, shows some interesting data on what firmware releases iPhone owners are actually using... and it isn't always the latest.

iPhone users likely keep up to date more than almost any other smartphone platform on the planet simply because Apple and iTunes make it so drop dead simple to find out about, and install the OS updates. But even so, Sadun's article shows not everyone is doing it:

The data, covering one week and provided by Headlight Software, showed no one on 1.x (thank Jobs for that!), less than 2% total on 2.0.x, less than 7% on 2.1.x, 26.61% on 2.2, and a whopping 65.49% on the current firmware, 2.2.1 released January 27.

So two-thirds on the latest/greatest firmware, just over a quarter on the previous release (yellowsn0w unlockers accounting for some of that, we suspect), and few stragglers back in the stone ages of 2.0.

As important as this information is for developers trying to figure out how to target their requirements, we're also just plain curious. We figure TiPb readers are some of the smartest iPhone folks on the planet. So let us know, are you on the most recent iPhone OS 2.2.1 version, or are you deliberately staying on 2.2 for now? Anyone just not care about firmware and sticking with an older version that "just works" for you?

And how many would upgrade to 3.0 in a heartbeat the instant Apple dropped it?