Is in that any rationale to jailbreak the iphone anymore?

SDK is out and comprehensive, any reason why i'd want to jailbreak my iphone?

any apps only available for jailbroken iphones that aren't coming the "right" instrument?

Answers: Yes. Emulators. Themes. MMS. Porn.

Those are pretty much the reason why people would still jailbreak.

It's because three out of the four cannot be done surrounded by the SDK. And the last one is not allowed by Apple.