Personally, key word being personally, I would wait for the Nexus 8 because it will be an 8inch tablet and shouldn't be too much longer until it's released. So if you prefer stock android, rooting, an 8 inch tablet (slightly less than the 8,4 inch Pro), and don't mind waiting a little longer you should just hold off and get the Nexus 8. If not than the tab Pro 8.4 isn't a bad choice.
Personally I prefer the Galaxy Tab Pro 10.1, which I own, because if I'm getting a tablet I want an actual tablet, and one that'll make the features that come with it ideal such as the multitasking, which on a 10.1 inch is perfect (FOR ME the 8.4 made it a little too condensed and crammed). But if you think the 8.4 is the perfect size for you, and if you're actually going to benefit/make use of the features which come with it instead of rooting it and making it stock android, than yes get it because the Galaxy Tab Pro line is really nice!
Hope this helps!
Google Nexus 5
Samsung Galaxy Tab Pro 10.1