Yeah the serve is a big part of his game, but he mainly makes massive use of it on clutch points. His game variety is great, fantastic drop shots, great forehand (when on) and an underrated backhand. I think he does need to work on his forehand though, as it's so flat, there isn't much room for error, and he often struggles with errors.
Yeah the forehand seems to either be really great or be very error-prone. I like his variety too, he's an interesting player to watch - some of the drop shots he did in Paris were amazing. Apart from Rotterdam and Auckland he's lived up to his seeding this year which is impressive - a dip in form after Paris would've been understandable.