Nick asked the question in his iPhone feed, so I thought I'd start a forum entry to see how people feel about having the iPhone app as iOS5 only.
I don't have an understanding about what benefits iOS5 will bring to the app, but I think that anything that makes it work better and smoother can only be a good thing. Using the latest features should make the app better and also a bit more 'future-proof' than if it is developed for an OS already over a year old.
Although iOS5 has only been out a few days, the app won't be ready for some time still and so, by the time it is released, the OS will be a lot more common than it is now and may even be a couple of sub-versions older as well.
What are other people's thoughts? Are there any solid reasons why this shouldn't be made iOS5+ only?