Do the job well... in gym
At first it looks as a great improvement over Reverso 3 - has a big binner hole for releasing a second in auto-block mode and much lighter.
Probably you don't want to take it outdoors - it's soooo light, aluminium alloy walls are soooo thin, overall it feels soooo fragile so I bought the spare Reverso 3 for my outdoors adventures. I do not trust this ultralight design - feels like it would be broken after the first contact with rock.
Disclaimer. Yes, I understand that "feels and seems" are not about the Reverso 4 but about my perception. Anyway I would never use any climbing hardware I do not trust and this review reflects my subjective opinion.
Anyway it's a cool belay device and a good example of a well-done engineering job (perhaps, too-well-done). If you feel comfortable with Reverso 4 it would serve your belay needs. Just never drop it on a hard surface even from you waist height.