Engadget have done a hands on feature about the PSPs Little brother the Mylo.
Heres an excerpt:
Holy hot damn, we got us a Mylo up in this piece. Yes, unfortunately it's only a late prototype (we haven't actually heard of anyone getting a final production unit yet) but here she is, Sony's ever-hopeful ace in the hole to get a foothold in the pockets of disenfranchised Sidekick 'tweens everywhere (and maybe even some 770 user throwbacks as well).