If you're a student you can probably get office for $10 if your school is on the list:
Microsoft Home Use Program - Microsoft Office Professional Plus 2013. The software suite includes Word, Excel, PowerPoint, Outlook, Publisher, Access and more!
If not, you should still be able able to get the student edition for a lot less than $450.
I've got 11 thinkpad tablets and have not had issue with build quality on any of them, and my guys use them on construction sites. The reason some of them have stickers is that they sold trackpads in different markets to meet demand which means they had to add regulatory notices. If it bothers you then just peel off the sticker.
Multitasking is definitely a problem if you are trying to use this as a laptop or desktop replacement. It will handle running multiple metro apps well enough, but if you are running multiple desktop programs it will definitely slow down. If you go into performance settings and cut down graphics options (do not render windows while dragging, etc...) it will help a help a lot, but its definitely noticeable. If I am running Outlook on the desktop I can't do much else except for light browser usage, if I run Outlook and Word at the same time it is noticeable. You don't want to have things open on the tablet if you are not using them, its not a workstation. In your example of split screening, based on my experience you would have no problem running Skype and Twitter or Facebook, but if you were doing that while you had things open and using resources on the desktop side you would definitely notice performance loss.
If you really need that kind of performance you should either get a tablet with a real (non-netbook) processor (i5, i7, etc...) or wait for Haswell tablets. If you are okay with reduced performance to get the long battery life (and its definitely long on this device) then the Thinkpad Tablet 2 is my favorite by a wide margin, and I tried 3 or 4 similar devices before I purchased 10 thinkpads.
tl;dr- its a great second device but you will notice performance issues if you try to use it as a laptop replacement
If you do get a thinkpad tablet 2, I highly recommend this case:
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Poetic HardBack Case for Lenovo ThinkPad Tablet 2[/h][TABLE="class: product"]
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$16.95 [/TD]
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Amazon.com : Poetic HardBack Case for Lenovo ThinkPad Tablet 2 10.1" 64GB Win 8 Pro Tablet Black (3 Year Manufacturer Warranty From Poetic) : Cell Phone Cases : Computers & Accessories