I think the OP has a good point.
Apple had it right when they started with the iPhone OS for use on their tablet. They problem is that's exactly where they stopped. It's the same OS that debuted with the iPhone in 2007, third-party apps not withstanding (the OS still functions the same). If you look at the history of operating systems, new versions with significant changes are released about every 3 years. Windows 2000, XP, Vista, and 7 were all released within the last decade. On the Mac OS X side, there are major differences between Cheetah, Panther, Tiger, and Leopard.
Three years after the iPhone, not only is the OS due for a substantial update, Apple is launching an entirely new device! Nevertheless, the iPad has the same features, limitations, UI, and embarrassing grid of icons as the original iPhone.
The iPad is supposed to do the basic computing that the average user spends most of their time doing. The problem is that the basic tasks users perform on a computer go beyond browsing the web, checking email, and using an app. There are some very common and basic tasks that users do everyday with their computers:
1.) Print. Users print documents from a variety of programs on their computers.
2.) Manage files. Users save and manage their own documents on the computer everyday. It's not about browsing every directory and system file on the hard drive. It's about accessing their own files which they copy, organize, rename, email, and delete.
3.) Connect USB devices. Users connect all types of USB devices to their computers, especially thumb drives for easy file transfers. The beauty of USB is that you just connect the device and it just works because all the necessary drivers are loaded automatically.
4.) Download codecs and driver updates. When users come across media, etc. that the computer doesn't support, usually the necessary components will be downloaded automatically, transparent to the user. This allows the device to stay current and not limit the user to a predefined set of supported formats.
5.) Multi-task. Users are used to opening multiple programs at once, but more importantly, they are used to switching back and forth between them very quickly.
All these things are simple tasks that users perform everyday. Support for certain things through apps is not enough. The worst part about the lack of support for anything like this on the iPad is the fact that it could be added without adding any complexity. In fact, ignoring multi-tasking, the entire UI could remain unchanged and the iPad could still support everything on the list!
As users browse the web or maps, they are going to want to print them. They are going to want to download files and save them. Safari on the iPad doesn't even use tabs!
As users check email, they are going to want to save and work with attachments (not just pictures). They are going to want to receive mp3 files and play them. Hell, you can't even add attachments from within the iPad email client!
As users create documents in iWork, they are going to want to print them and save them to a thumb drive. They don't want to have to email themselves or sync them through iTunes.
They are going to want to do stuff in the foreground while they get a message to their IM client in background. They don't want every message to pop up on their entire screen as a Push notification.
It is such a shame that Apple didn't build upon the iPhone OS when they launched a new device with a tablet form-factor. As it stands now, the iPad can't be considered a tablet computer. Although it does some basic computing tasks that the average user spends most of their time doing, it doesn't have support for features that come along with those tasks.