If you absolutely cannot take time off from a Monday-to-Friday job, then a weekend DMV slot is worth the effort. The convenience is the single biggest advantage.
The main challenge, however, is actually getting one. These appointments are extremely competitive and vanish almost instantly after they are posted online. You should also not expect a less crowded or faster experience once you are there. The value is entirely in avoiding a weekday visit, not in a quicker process. It really boils down to a trade-off: the hassle of booking a rare Saturday slot versus the difficulty of scheduling a weekday trip.
Whether a weekend DMV slot is worth it in New Jersey really depends on how much you value not taking time off from work. The main benefit is obvious: it saves you from using a vacation day or losing pay.
The reality, however, is that securing one of these appointments is extremely difficult. They are in incredibly high demand and get booked almost the instant they become available online. You need persistence and a bit of luck, often checking the NJ MVC website repeatedly at specific times. Furthermore, not all services are available on Saturdays, so you must first confirm your transaction can be completed on a weekend. Even with an appointment, expect the agency to be very busy.
If you can successfully book a slot for a simple transaction like a license renewal, it can be a huge convenience. For anything more complex, or if you get easily frustrated with online booking systems, a well-planned weekday visit might prove to be less stressful overall.