Notion Ink will begin taking pre-orders for its Adam Android tablet on Friday, but there are still several reasons to be skeptical of the once-highly-anticipated device.

First, the basics: Adam is a 10.1-inch tablet running Android 2.2 with a custom interface on top. Although this version of Android will soon be outdated -- Google just announced the first Gingerbread (Android 2.3) smartphone, the Nexus S, and details on the tablet-centric Honeycomb (Android 3.0) are starting to trickle out -- Notion Ink says it has already developed advanced features on its own. For example, the Adam supports VoIP calling and allows users to arrange multiple apps on the screen as tiles.

Other technical specs include a dual-core Cortex A9 processor, Nvidia Tegra 250 graphics, 8GB of flash storage, a microSD slot, two full-size USB ports, one mini-USB jack, HDMI and a 3.2-megapixel camera that swivels from front to back.

The kicker for Notion Ink's Adam is an optional Pixel Qi display, which includes a black-and-white reflective mode for outdoor reading. With this display, the Adam costs $500 for a Wi-Fi model and $550 for Wi-Fi and 3G. You can also pick up an Adam with an LCD screen for $375 (Wi-Fi only) $425 (Wi-Fi and 3G).

This all sounds pretty good, especially considering the pricing undercuts (or rivals) that of Apple's iPad. However, we still have some questions.

Android Market?

Notion Ink has not confirmed whether Adam will support the Android Market. The reason we don't expect this as an automatic "given" is because the company has previously spoken of building its own app ecosystem. We know the tablet will have a web browser, e-mail app, e-reader, calendar, and music player (as native applications), but without Android's growing app library, the Adam's usefulness will be limited compared to other tablets.

When Will We See It?

It's hard to tell what the Adam will be like without any videos of the final product. There are plenty of nice-looking pictures and claims such as, "fastest tab switching we've ever seen," but there's no hard proof that Adam works as advertised.

Also, the Adam's ship date is still a mystery. That's right, they're taking pre-orders for what is technically still vaporware.

While Notion Ink's fans -- the company blog does have a dedicated following -- may not mind plunking down hundreds of dollars for an I.O.U., most people should let this pre-order period play out until Notion Ink fills in the missing details.