What kind of beetle is this? Beneficial or Pest?

Your Scarab guest is an adult Spotted Grapevine Beetle, Southern Variant, Pelidnota punctata, and they generally dine on wild & domestic grapes & grape leaves, and generally arenot a serious pest of grapes. The adults are about 25-28mm in length, and the grubs/ larvae, which feed on rotting wood and live underground for a year, grow to 45-50mm long. They're fairly strong flyers, and you might sometimes see them around lights at night. They're found in Central to Southern Eastern North America. They may be very mildly pesty, but the grubs are mildly beneficial. Good question and good clear illustration! Your Scarab guest should be fine in the backyard (unless you're growing grapes), and grubs could be beneficial by consuming rotting underground wood.