One negative: With all that hardware it’s almost 3 times heavier than the Nintendo Switch, which is already near the upper limit for holding comfortable for longer play sessions.
edit: On closer look that's comparing the Switch without controllers (297g) to the Steam Deck with controllers (669g). The Switch with controllers is 398g, so the Steam Deck is only ~1.7x times as heavy - though that's still a lot of extra weight to hold in your hands.