I've only had the tablet for a few weeks, but I'm pretty sure the tablet incarnation of Android is probably 80% of what most users need in a workstation. I'm not most users, but I figure: hook up a big screen and a real keyboard. Create some key bindings to replace most of the gestures, and write a few pieces of software to handle document production, presentations, and spreadsheets in a slightly more robust manner, and you're basically there. I wouldn't give up my laptop today for a tablet, and I think the platforms still have a ways yet to go, but that's not insurmountable.
Prediction: in the next decade, we'll see embeded tablet-like devices begin to replace desktops computers for some classes of use and users. General web surfing, reading, quick email, and watching videos on YouTube seem like the obvious niche for now. I started to explore this in "Is Android the Future of Linux," but it's not abusrd to suggest that Android or iOS like devices might begin to address more "general purpose desktop computing."
I want to be clear: we're not there yet. These systems aren't versatile and fully featured enough to keep up with full time use on an extended basis. This is mostly an application/software problem. As applications evolve and as more functionality moves to remote systems anyway (this is the "cloud," we've heard so much about,) tablet operating systems will seem much more capable for general purpose work. Better mobile productivity software will help as well. Eventually, I think Android and similar platforms will have a shot at the desktop market for most usage because:
IT departments will get a lot more control over intra-organization information flow, which could save a lot of money for various IT categories: administration, support, and data protection costs.
Behind the firewall dropbox-like services, and creating some sort of centralized workstation configuration management (which makes sense for a flash based device,) means backups can happen automatically, and if devices need to be re-imaged or are lost or damaged, it only takes a few minutes to get someone back to work after a technology failure.
Limited multi-tasking ability will probably increase productivity.
Disconnecting keyboards from the screen will probably lead to better ergonomic possibilities.
Eventually, it will be easier to integrate Android-like devices with various workflow management/content management systems.
The technology needs to mature and workers and IT departments need to become more comfortable with tablets, without question. Also, there are some fundamental developments in the technology that need to transpire before "desktop tablets" happen, including:
Split screen operation. There are enough "common tasks" that require looking at two different pieces of information at the same time that I think tablets will eventually have to give up "full screen everywhere," operation. Conventional windowing is unnecessary, and I don't think anyone would go for that, but displaying two different and distinct pieces of information at once is essential.
Better "Office" software for spreadsheets, presentations and document preparation. A necessary evil.
Behind the firewall (preferably open source) solutions to replace services like Dropbox/Box.net and whatever other services emerge as essential parts of the "tablet/smartphone" stack.
VPN clients and shared file system clients that are de ad simple to use. I think these are features for operating system vendors to develop.
Thoughts? Onward and upward!