Ranked in these QuestionsQuestion Ranking
Pro Great pen support
The (included) Surface Pen has a very interesting set of features - it allows for 1024 points of pressure, has an eraser on top, and when you click the eraser it will open Cortana (Microsoft's new voice assistant). It's magnetized, so it will stick to the left side of the Surface. The Surface achieves all of this via its new N-trig technology (replacing the Wacom technology found in older generation models). There's also palm rejection technology, so whenever the pen tip it close to the screen is will ignore all finger or palm touches.
Pro Laptop-level specs
The Surface Pro 4 comes in configurations from core M up to a core i7. RAM starts at 4GB, and goes to 16GB. Storage caps out at 256GB of SSD storage, which should be enough for most users. These are all specs that can be found in most laptops - even beating out some budget-midrange desktop options.
Pro Good expandability options
The Surface has a USB 3.0 port that can be used for a mouse to be plugged in, or you can plug in a USB hub or Microsoft's own Surface Dock, which has 4 USB 3.0 ports, audio output, Gigabit Ethernet, and two HD video ports. The Surface Dock allows for as much expandability (or more) as most laptops out there. There's also a SD card slot if you need more storage (current SD card sizes range up to 200GB, although this won't be as fast as the internal SSD speeds).
You can find a computer with similar specs for about half the price of the Surface Pro 4. You are paying a premium for the high-end build quality, for the engineering required to manufacture a fully portable computer, as well as for the high resolution touchscreen.
Con Lack of touch-focused apps
Windows has traditionally been a mouse-and-keyboard operating system. Finally, third party apps are starting to become more touch friendly, although it's a long, slow process. The Windows Store still lacks many big titles, which means the only option is to download the regular Windows version of most apps, which are rarely touch-friendly.