oOple works fine on the iPhone. The lack of Flash and Java does limit its use on a lot of other websites though. Lack of Java could potentially be excusable (a JRE shouldn't be too hard to implement, but Java is not really widespread) but in a world where 99% of internet going devices have Flash... lots of websites don't feel the need to have plain HTML components to substitute for Flash. This creates serious issues browsing some sites with an iPhone.
So much so that the Advertising Standards Authority has ruled that Apple has misled consumers over advertising claims that the fact that the iPhone can display the "whole internet", which it can't. It's a real shame.
I've been playing with Google's Android platform which is due for release later this year and it's much the same story there. However trying to port stuff to work lower level I have found these devices are more than powerful enough, so I can't see an excuse.
I keep reading that Flash will be released soon for iPhone but I doesn't seem to happen? Windows Mobile however does support Flash, and there are some cool devices now by HTC, Samsung and others running Windows Mobile. These tend to be more powerful (hardware) in comparison to the iPhone also. (
Samusung Omnia - funny video).
Personally I think Andorid will be the best platform by far for mobiles, and devices are due to be released within just a month or two. Some of the Androids themes, comibned with it's powerful GUI tools mean it actually works as well as, or even better than, the iPhone - which I think everyone could agree has one of the best UI's around and is a current industry benchmark.
And to anwser the IM question, yes the iPhone supports it but through stuff like Meebo and basically web based approasches. Maybe with the app store (Apple finnally released an SDK!) there will be some native programme for these. For Windows Mobile - there are already lots of native programmes to use for various IM services. I'm not a fan of the iPhone, it has a great GUI but there are still things that let it down. The cost is just the last straw for me, but I certainly can see why others are interested.