Just throwing my hat into the ring here: I'm on my 2nd SP2 but only because I upgraded from the 4200U to the 4300U. It may be luck or that forums tend to be biased toward negativity (most people only go to forums because they have a problem), but I have not had any hardware problems and only a few limited software bugs that were easily fixed by rebooting. I did, however, suffer from the Dec. firmware fiasco but fixed that when I exchanged for the 4300U. Best tech device I have ever used, including most of Apple's devices and a few Android tablets. I find that Windows 8 is the best version of Windows ever created (not considering their historical significance but functionality): it marries the simplicity and convenience of smartphone apps but let's you get under the hood and use all of your serious programs that you already own and the wealth of open source software available. This gives it a versatility that really shines with the SP2, whether acting as a tablet or a full Windows laptop, which might be the kind of hardware they were designing the OS for.
Getting to the original question, the considerations that I had to decide to get the SP2 were the following: I wanted something incredibly portable that could be used as a tablet for reading and note taking with a stylus but also packed with enough processing power, graphic power, and RAM to multitask like a fiend. As a research scientist, a major scenario that I could see myself using the device for would be writing a paper in Word while analyzing data in Excel and CPU-intensive curve-fitting software, having both Photoshop and Illustrator open to make figures while having my web browser open to 10 or so tabs and maybe 5-10 pdf papers open while listening to music. This usage might exceed the 4 GB of RAM that most of these Windows tablets have, not to mention the limited 128 GB of SSD that most have. The SP2 is also ~60% faster than those with the Core i5-4210Y when considering the Core i5-4300U CPU in the newer SP2s. Its 10.6" tablet form factor at 2 lbs (2.5 lbs with Type Cover 2 keyboard) was highly attractive for me so that I could bring this device anywhere without having to plan to use it since it is so small and light, which has come in handy a few times already. I use it to take notes in seminars with the stylus in portrait mode on my lap, which is great when there are no tables, or flat on the table as I would a sheet of paper. When I need to type or just don't want to hold up the tablet, the 2 position kickstand is such a game changing feature which makes it both easy to use on my lap and on a desk. Contrary to what others may say, I find the SP2 Type Cover 2 is rigid enough for rapid typing on your lap (not sure about Type Cover 1).
I'm also quite a gamer and having the ability to play modern games on the go (albeit at lower res and detail settings than I'm used to) is amazing. Playing heavily modded Skyrim plugged in at my work desk with a mouse when working on the weekend is awesome. XCOM: Enemy Within on my lap on the subway using the Type Cover keyboard and the stylus for mouse is even more awesome. Don't have a seat?: I play Civilization V in its touch-enabled mode and take off the Type Cover to reduce the weight since I'm usually standing on public transit. Most other Windows tablets are not powerful enough to give you a good experience with these games. You can also play classic games (such as from
GOG.com) which would also run on the weaker tablets but not the Android ones.
So, yeah, that was my thinking when I decided to get a SP2 versus other tablets. I would have gotten the SP1 except that its battery life sucked and the Intel HD 3000 GPU was still terrible. These were fixed by using the Haswell processor while also massively increasing the GPU power to an acceptable level with the HD 4400. Personally, I can't say much about the tablets that aren't out yet and, since I got the SP2 in December, I haven't really been keeping track of what's on the horizon. In summary, the SP2 is my tablet of choice because of full Windows 8.1, powerful CPU and (relatively) GPU, larger SSD if you want, Wacom digitizer for accurate and pressure-sensitive stylus, superior kickstand, and more RAM option which would allow me to effectively multitask an intensive array of programs like a laptop while also bringing the conveniences of the touch tablet experience.