Saying GarageBand is a toy is like saying iMovie is a toy. It is an entry-level recording/sequencing/loop program geared toward musicians who are computer-recording novices.
Just as a good editor can put together a very nice project using iMovie, a good musician will be able to make decent recordings with garageband. If you know how to import and export midi - and need to do so regularly - then you're not who this program was created for.
As others have said, I'm sure Apple intends to add many more features as the product matures. Just don't expect it to ever compete with a "Pro" music tool.