SD slot would be very nice, but as a portable device (which the iPad definitely isn't, for me) this is very easy to justify. I think we can now see why Microsoft went early with Surface, even though they didn't have anything people could use.
iPad sales are unlikely to be affected by either, but MS's bottom end Surface is now in trouble IMO, and the Fire is DOA for the rest of the world. Assuming, of course, the 7 is as good as it ought to be. Asus may be pushed hard to maintain Apple style Q&A, and there isn't the margin (any margin?) to give Apple style customer service.
Interesting times.
PS I like the form factor. I'd prefer 4:3 because it's just so much more comfortable in portrait mode (where I prefer to browse and read content) and I only watch TV/movies on my TV. But 1280x800 is much better than the typical non-Apple displays out there.
PPS Of course it never makes sense to buy the first generation of anything, but I'm still tempted.