I saw WORLDS FINEST #1 at the comic shop. Had a not so flattering Perez cover with the ugly designs. No biggie though. Half of the issue is supposed to be Maguire, so that alone is worth it.
BUT...Maguire only does some pages in the middle of the book, and it looks like Perez does the majority of artwork. This kind of sucks because despite the above image, Maguire's part shows a Helena Wayne in a Robin outfit, and a superbly redesigned Supergirl. Perez gets to draw the ugly new costumes, and he doesn't manage to draw the two leads as nicely as maguire.
Maybe they'll alternate issues between who does the majority for each one, but I ended up not buying the first issue. But damn, Maguire is one of the few artists from the 80s who's art has gotten even better after all these years.