For those that need the power of a desktop in many locations, often a laptop or a tablet PC is the way to go. Even just a few years ago, laptops cost several thousand dollars, but prices have fallen rapidly which have opened the market up to a much larger audience.  College students, IT admins, Road Warrior salespeople, and others can purchase enough computing power for their needs.

Current debates have been raging about whether to buy a laptop or a tablet PC.  Tablet PCs are often smaller, have touch screen, and fit in a backpack easier than a laptop. This is great for simple applications such as receiving email, browsing the web, or other tasks. 

For more powerful applications such as graphics software like Photoshop or development software like Eclipse, the laptop is still the preferred way to go.  The laptop is bulkier and takes a little bit longer to get set up, but it comes with a larger screen and keyboard to work with.  It also generally has a better processor, more RAM, and a larger hard drive.

Another benefit to using a laptop is that it's easier to fix and replace an individual part such as the laptop screen. If a tablet PC has a problem, the entire unit often has to be replaced.

To summarize, if size and convenience is your primary objective, a tablet PC may be the right thing for you.  If processing power and a larger screen size is more important, then stick with the laptop.