Hmm, don't want to dampen your Intel-lust (
I'm kidding!) but R.Pi isn't exactly a secret and has been getting increasing amounts of "buzz" for a considerable time now. So there's definitely been time for Intel to push something they were planning to do anyway.
I remember folks saying that Intel got slightly wrong-footed by VIA's Mini-ITX and smaller form factors - a "mistake" that they're not going to repeat. So it's entirely possible that NUC was already "on the boards" and Intel took the decision to announce it now to cash in on the current focus on small/cheap* computing, (* although as others have said NUC isn't exactly cheap), that's come as a result of the coverage of R.Pi.
So while the product itself isn't necessarily a reply to R.Pi, the timing of the announcement does look a little ... "interesting". But hey, if NUC falls in price (<£100 with the processor would suit me) then I'll probably buy one - as you say it's a darn site more capable than R.Pi.