The MacBook Air that I priced (from Apple's own website) had an Intel i5 and a Intel 4000 integrated graphics chip. The processor specs are pretty much the same for the Surface Pro, and the GPU is rumored to be the 4000 or its successor (granted we won't know for sure until full specs are released). Meaning, to everyone except fanbois, the two will perform about the same. If the Air can push a 2560 X 1600 external monitor... then the Surface Pro will (it's the same hardware). If the Surface comes around $1000 then it will offer the same basic performance as a lower-end Air for the same price... but in a different form factor. That form factor might be a serious selling point for businesses.
No offense, but I don't care what you think of when you hear "workstation"... especially when you start comparing the Surface Pro to MacBook Pros that will probably cost between $200 and $1200 dollars more. I know several businessmen whose office provides them with both laptop computers to use as workstations (with a single 20-22 inch LCD monitor... they aren't in software development) and tablets to use on the factory floor (or elsewhere). I'll bet those businesses would jump at the opportunity to give them one piece of hardware that will do both adequately!
Businesses aren't interested in "flashy". They want solid (often middling) performance, at a bargain if possible. A tablet that seamlessly integrates with their existing systems and potentially replaces separate units might be attractive (we'll see)...
Except that the Air likely has more RAM and faster SSD, you're probably about right.
If the Air can push a 2560 X 1600 external monitor... then the Surface Pro will (it's the same hardware)
The missing hardware on the Surface is called Thunderbolt. In the Mac's case it carries DisplayPort signals. The Surface only has HDMI, which probably means max 1920×1200 at 60 Hz, if even that is supported. As a tablet, the Surface is meant to display your movies on a big TV, not to have a big monitor set up, so support for that is up in the air right now.
No offense, but I don't care what you think of when you hear "workstation"
A workstation usually means a higher-end computer, as opposed to just a regular desktop. For the more purist definition, you're usually talking server-class hardware -- ECC memory, Xeon processors, option for dual processors, etc., and you're into CAD, a pro graphics card.
They want solid (often middling) performance, at a bargain if possible.
One reason Mac notebooks sell so well. They are very solid and sturdy. Unlike most of the competition, they don't feel like a toy. And good businesses don't think purchase price, they think TCO. Macs have always had a lower TCO even if the purchase price was higher.
A tablet that seamlessly integrates with their existing systems and potentially replaces separate units might be attractive
That is a likely use case.