question : can you search exchange emails?
Yes, Mac OS X Spotlight search is a key part of the 3.0 iphone software. That will search everything including e-mail.
This will include e-mails that may have not been allready downloaded in a certain file and search exchange remotely.
The reason they leave out these features which arguablly, should have been there from the start, is that you can change the phone any time, without having to buy a new phone. The whole original concept of the iphone was that if you had to bring a new feature out, you would have to put more keys onto the phone. That isnt practical.
Its so easy to forget this is their first smartphone and they are doing and amazing job in a sensible steady manor.