Australia, New Zealand & the South Pacific - Visiting Milford Sound after Milford Track?

Hello-
I'm planning to do the Milford Track in late Summer. It ends at Sandfly Point, with a ferry to Milford Sound by 4pm. Is it worth staying overnight in Milford Sound to do a cruise through the sound the following day?

If it makes a difference, I will be starting in Queenstown and taking a bus to Te Anau/Te Anau Downs, hiking, ???, and then back to Queenstown. I only have a 2 weeks (maximum) in New Zealand, so I'm not sure how much I can squeeze in on the South Island. Will probably spend 1 day before/after in Queenstown as a buffer in case of weather (do I really need this?) and then a few days on the North Island or Christchurch.

Weather is better in late summer, but when I was there in late spring it was quite cold and foggy ... staff said flights into Milford had not been able to operate for the past 2 weeks due to fog, so this is typical at times. It is a rain forest after all. Very beautiful area even in the fog and the cruise wasn't operating that day, either, but my impression was that the cruise is just more of the same and I didn't feel deprived. Now some of the other cruises (that are more remote) would be interesting, but Milford is a bit busy for wilderness.

The North Island is completely different and just as interesting (though everyone rave's only about the South Island generally). Personally I found the volcanic features more interesting in the North Island, also the drowned kauri forests in the far north (even the "boring" flat parts of the North Island have great scenery and attractions -- NZ is an amazing place, there are no bad parts except in the cities).

When you say it's "more of the same" -- do you mean it's the same as the track or just the general are? Did you get a chance to do the track?

More of the same further down the sound (only accessible by boat) as close to the "sound head" (the part accessible by foot). Definitely do go to the Sound (I think you don't have a choice unless you are walking out). I didn't want to do the trek but it is often sold out a year ahead, bookings are rather essential for the walk unless it has changed in recent years. What I did do is drive from Te Anau to Milford sound rather than go by bus, and this allowed stopping at a dozen points of interest along the road -- some quite special indeed. A beautiful road with some astonishing creeks and rock formations nearby.