Price plans are in line with or cheaper than other smart phones.
Safari web browser blows away any other CELL phone browser in existence. I'm sure there are folks that prefer Blazer or something, but Safari is pretty much universally accepted as the current state of the art.
Sites that incorporate flash or java coding are not going to work. I suggest that sites which incorporate those technologies in the login area are poorly designed. Safari is a standards compliant browser. Are you sure that your company doesn't have a mobile compliant website (akin to google's m.google.com)?
There are at least 3 applications which allow you to do that on the app store NOW. Files, Datacase, and FileMagnet. Dozens of apps are being added daily.
No phone is everything to everyone. With the app store, the iPhone is pretty much more than enough for most people.