Early reviews of Microsoft's Surface tablet computer are beginning to appear online. Though they are mixed, a common theme is that the hardware design is impressive, but the software is a concern.

Microsoft's Surface is designed for a niche between an iPad and a Windows-based laptop. It ships with only a touchscreen, but with a $100 carry case that includes a physical keyboard it can expand to function like a conventional laptop.

The Surface goes on sale October 26, the day Windows 8 is officially released.

The first models will run Windows RT, the special version of Windows 8 designed specifically for devices that run the same energy-efficient processors found in smartphones and tablets. This allows for a reported nine-hour battery life.

Surface tablets running the full-blown Windows 8 operating system won't hit the market for another few months.

Surface Passes Physical Examination

Early reviews have praised the Surface's physical design. For example, even without the keyboard case, the Surface has a built-in stand at the back to prop it up -- useful when watching a movie with no need to type. (Source: engadget.com)

Those who've tested the Surface are also impressed with its lightweight though resilient construction. Reviewers noted the device provides the largest screen possible without making the device too bulky.

However, several reviewers note the screen's resolution isn't as high as the new iPads, so video and graphics don't appear quite as sharp.

As for software, Windows RT starts up almost instantly. It runs well for casual use, such as web browsing. But trying to run multiple applications simultaneously (such as Microsoft Word and a browser) can produce sluggish performance.

App Shortfall Limits Usability

The Surface's biggest limitation is that Windows RT allows users to add applications only through the official Windows Store. That's a problem because Microsoft has not convinced enough developers to build applications for it. (Source: go.com)

Several reviewers suggest people considering a Surface may want to wait a few months and see whether the forthcoming models running the full version of Windows 8 better suit their needs.