Yes of course you can make non Cocoa apps for OS X that feel very "OS-X-y", but I for example need my apps to be able to handle Japanese and German Umlauts at the same time, and since many programmers just seem to completely forget about internationalization of their apps (I'm happy enough if the Umlauts don't get mangled) this is often the point where most non Cocoa apps become useless for me, because the programmer simply has to make an effort to make Unicode work there, and most of them just don't bother.
With Cocoa Unicode support is par for the course (there are exceptions, very bad ones...). Apart from that I know many non Cocoa apps that try to look like good OS X "citizens", but very few of them really can convince. Also all of the Cocoa goodness you get more or less "for free", the programmer needs to make quite an effort to support in other frameworks, like Services (which I use a lot), spell checking etc. And then there are the very handy tools which many Cocoa delopers use to add functionality like LinkBack or Sparkle. Which just make everything even more seamless.
by Kilian — Mar 22
With Cocoa Unicode support is par for the course (there are exceptions, very bad ones...). Apart from that I know many non Cocoa apps that try to look like good OS X "citizens", but very few of them really can convince. Also all of the Cocoa goodness you get more or less "for free", the programmer needs to make quite an effort to support in other frameworks, like Services (which I use a lot), spell checking etc. And then there are the very handy tools which many Cocoa delopers use to add functionality like LinkBack or Sparkle. Which just make everything even more seamless.