It seems really awkward to have that new interface side by side with the old (tested and perfected) UI.  I thought Media Center was bland and useless, but this seems like taking Media Center, iOS, and Windows 7 and smashing them all together. 

But then again, it could be the best thing since sliced bread.  It is a little too early to draw large conclusions.

Wait, what?  I don't get it.

Neat!  I don't know lua and I don't have an Nspire, though. 

If I want to create a BASIC-Program, which should contain sound, I'll have to use Axe.
BUT how to create a program with sounds, if it should run on a TI-84+ without any special APPs, too?  

If you compile a program in Axe, you should be able to run it among all 83+ family calculators without the Axe app.
Axe is a compiled language, meaning that the parser reads your source file and creates an Asm program.  You can run that Asm program on any calculator without the parser (given that your program does not need a shell).

Maybe I need to sent 2 PRGMs to another TI:
One BASIC-program and one ASM-subprogram

In order to run an Asm program from BASIC, you use "Asm(" (without quotes) followed by the name of the program.

But I've never learned ASM-programming, just Basic.  

You don't really need to know Asm to make a program in Assembly; Axe compiles into Assembly.  Well, if you really want to learn Asm, Hot_Dog made a wonderful, well-worded tutorial.  http://www.omnimaga.org/index.php?action=downloads;sa=downfile&id=594

If you would like any clarifications, feel free to ask.  
BTW, welcome to Omnimaga!

Looks really nice!

It sounds promising, but I would not jump the gun too quickly.

The gameboy is also a Z80, so we can also make epic beats.