Update: for Apple's latest (4th generation) iPad, please refer to our comparison of Microsoft Surface vs. iPad 4.
Microsoft execs must be biting their nails. With the iPad eating into the desktop PC market, Redmond knows that it needs to establish itself as a serious player in mobile. With Windows Phone struggling, Redmond's best hope lies with its self-manufactured Surface tablets.
Surface presents an interesting alternative to the market-leading iPad. Is this Microsoft's first step in dethroning the king, or will it fare no better than the ill-fated Zune? Let's see how Surface RT stacks up next to the third-gen iPad …
Dimensions

The first thing you'll notice is that Surface is meant as a landscape tablet, while the iPad's primary orientation is portrait. Microsoft has constructed a beautiful tablet that – unlike some competitors' devices – doesn't look like a blatant Apple rip-off.
Surface RT is longer than the iPad, but more narrow. This can be traced back to its display's more oblong 16:9 aspect ratio as opposed to the iPad's 4:3 display.
Weight

Surface is a bit heavier than the iPad, but not by much.
Display

This is a huge advantage for the iPad. Its market-leading Retina display blows the Surface's screen out of the water. In 2012, Apple upped the ante for tablet displays, and the specs of the Surface display are stuck in 2011.
Processor

At least on paper, Surface comes out looking good here. Its Tegra 3 chip is quad-core, with a maximum clock speed of 1.4GHz. Apple opted for dual-core processing (but quad-core graphics) in the latest iPad.
RAM

Here's another good sign for Surface's performance; its RAM doubles the 1 GB found in the iPad 3.
Storage

For the same entry price, Surface gives you twice the storage. If you like to store lots of movies, apps, and games, Surface gives you ample space.
Battery

Take these numbers with grains of salt. Though the iPad's battery hardware is better, remember that it's driving a display with three times as many pixels. We'll have to revisit this after getting our hands on a Surface, but uptimes could end up being close.
Wireless

Microsoft opted not to sell a 3G or LTE enabled version of Surface, so it's all Wi-Fi. With many of us toting smartphones with hotspot capabilities, this won't be a deal-breaker for most – but Apple does give its customers the option of paying more for 3G/LTE.
Cameras

Surface's cameras are still a bit of a mystery. All Microsoft is saying is that the front and rear-facing shooters are "720p HD." This could mean the cameras have under one megapixel a piece, or it could mean they have more.
The iPad's cameras, meanwhile, are a known quantity. Don't expect anything phenomenal, but the 5-MP rear camera is roughly (if not exactly) the same as the one in the iPhone 4.
Intangibles

This is where things get intriguing. Microsoft is marketing its device as a more productivity-focused alternative to the iPad. Its optional keyboard add-ons are a big part of this. The Touch Cover is like an iPad smart cover, only with built-in pressure-sensitive keys. Will it help you to get stuff done? Probably. Is it worth paying an extra US$100 (bundled) or $120 (as a separate purchase)? That's a tougher call.
Surface also ramps up the productivity quotient with a built-in kickstand and stock software. Combined with the keyboard, the kickstand lets Surface quickly transform into a faux laptop. Another potential plus is that Surface ships with RT versions of the Microsoft Office suite.
If we're talking apps, though, the iPad has the clear advantage. The iOS App Store easily houses the largest – and best – collection of tablet apps available. Meanwhile, the Windows Store (the only way to get apps on Surface RT) is fresh on the scene. It will launch with a solid selection, but it won't compare to what the App Store offers.
Also remember that if you want to use traditional Windows desktop software, you'll want to look at the Windows 8 Pro version of Surface; those apps won't run on Surface RT.
Summing Up
We have to admire what Microsoft is doing here. At the risk of alienating its hardware partners, it's introducing Windows 8 with its own beautifully-designed tablet. The company is swinging for the fence here; win or lose, that's always exciting.
The big question is whether customers will care. Sure, Surface has a cool new keyboard, but you can buy keyboard cases and accessories for the iPad. It has a kickstand, but there are many ways to easily prop up an iPad. In the most important category – apps – Surface has a lot of catching up to do. There are a lot of questions, and Microsoft's upper management may not be sleeping well for the next few weeks.
What do you think: is Surface going to be a hit? Or are we looking at Zune: Tablet Edition? Let us know in the comments.