If you're gonna ask if tablet is worth buying, the answer is: YES it is. I have the SM-P601 3G and I'm really happy with it. Out there, the new and available samsung tablet are pretty much the same as this one, except that ours include S-Pen.
The best part is Lollipop is coming to this tablet.
And it doesn't matter which official firmware you update to, the lag will always exist as long as it is Samsung's. If you don't want those laggy UI, flash custom ROM which I recommend this one (3G variant)
http://xdaforums.com/galaxy-note-10.../sm-p601-cyanogenmod-12-0-unofficial-t3052009
I am very satisfied with this tablet, and I'm not regret choosing this over Tab S 10.5 (or even the new tab s2). Right now, in my country, this note 10.1 (3g) is still more expensive than tab s 10.5 (without warranty) because of its popularity, no matter what marketing they made for tab s.