This definitely looks like a great move on Apple's part. In reality though for Nokia this isn't really a battle between Maemo and iPhone OS but really between the iPhone OS and Symbian. I love my Symbian phones and have actively used them for about 5 years now, but this has to worry them. The iPhone user base is much more apt to purchase applications for their phone and catering to the Enterprise market is key for widespread adoption, you know that every executive is going to be asking his IT department for this phone.
Most Symbian phones are almost sold as dumb-phones my friend had a 6682 for a year without knowing you could install any applications. The N-Series as well are sold as multimedia phones and not really as phones you can add stuff to. With the iTunes store the iPhone is going to have a HUGE advantage over the current distribution methods that Nokia uses. We'll see how all this shakes out with Ovi and all that but I must say kudo's to Apple for delivering what looks like a super interesting platform. (ps. I am usually an Apple hater)