The band was awesome! They blew everyone away.
What does this mean? Surely it does not mean the band actually blew everyone away. But it seems to mean something good?
The Free Dictionary, in its article for to blow has the following definitions:
blow away Slang
2. To defeat decisively.
3. To affect intensely; overwhelm: That concert blew me away.
I guess, it's exactly the meaning you need.
It means something good; in fact, blow [someone] away means leave [someone] greatly impressed.
Do note that there are quite a few other meanings for this expression (it might mean kill someone by gunshot or get rid of, for example).