Is Nusa Penida worth visiting from Seminyak?

You might want to consider visiting the Bird Park. It's a pleasant place to walk along the boardwalk, and it's not too far from Seminyak. You could also try visiting a beach town that's a bit more laid back than Seminyak.

Your experience on the island will depend on how you plan your trip. If you're doing it as part of a guided tour, you'll likely encounter crowds, but if you do it independently, you might have a more relaxed experience.

I'd advise against visiting Nusa Penida from Seminyak. It's a grueling 12-hour slog, and the crowds and heat can be overwhelming. You might be better off exploring Seminyak and its surroundings instead. If you want to see dramatic cliffs, you could try visiting Uluwatu again, and if you want to experience lush nature, you could visit Ubud again. Seminyak has its own unique charm, and it's worth appreciating that.