What IPhone OS do you build for when releasing?

There are currently 3 options. 2.0, 2.1,2.2. My app only needs 2.0. Do I build for 2.0 or 2.2? What is the best option?

From stackoverflow

• I'd build for 2.0, working on the assumption that you'll get a bigger audience that way as you'll also catch those people who for various reasons cannot be bothered to update the OS...

• Build for the minimum OS version your app needs to run. If you're not using anything that was introduced in 2.1 or 2.2, build for 2.0.

  Keep in mind that while most iPhone owners will automatically update their OS when they sync and iTunes tells them to, iPod Touch owners have to pay a fee and may be reluctant to upgrade.

  There's no sense in limiting your potential client base, so choose the oldest OS version you can.

  Ryan Townshend : Touch owners have to pay a fee to update? Hows that work? State your source please, I want to know more.

  Hunter : Apple has traditionally charged upgrade fees for iPod Touch owners, yes. They did this when they released 1.2 and again with 2.0. Basically anytime they delivered a bunch of new features. I believe it was a $10 upgrade each time.

  Hunter : Oh, it's done via iTunes, just like purchasing a song or whatever. http://www.apple.com/ipodtouch/softwareupdate.html

• I agree that you should think carefully about building for the most possible people but there are some things that don't work quite right if you build for say, 2.1 and then run on 2.2 or 2.2.1.

  The biggest example I can think of:

  If you use grouped tables with centered text and build for 2.1, it will come out left aligned on 2.2 and 2.2.1. I filed a RADAR on this issue.

  Basically, make sure you test on as many combinations as you can - there are subtle problems like that.

• Always best to build for the lowest common denominator your testing allows.

  If you can test on 2.0, 2.1 and 2.2 then you will reach the most people that way. If you can only test on one release, you should use the one that covers the most people - probably the latest considering Apple's agressive upgrade mechinism.

  What you should not do (as Hunter implies) is build for one release and assume it will work on others.