I've both here at home and used the Ananda for nearly a year. It's a great can at everything, even at soundstage. Interesting i was asking me the same and got a brand new HD800s for around 1100 bucks. I couldn't resist it.
After some days of ownership and a/b comparing i am to sell my Ananda. Short answer, yes, it is worth it for me, absolutely! The only thing the Ananda has is a deeper reaching low end due to obvious advantages of planar technology in this regard. But the Sennheiser 800s is no slouch here too, with a extremely well textured low end which is very fast (i'm on solid state amp).
In all other areas HD800s is clearly better. This is the most transparent, most detail retrieving can i've heard and i don't think it can get (much) better than this. Imagine this world of details painted in the largest room you'll probably hear on headphones and that's the hd800s like.
Highly recommend it!