The one issue that I have with Zanzibar, based on what I have heard is that's it not a particularly unique experience - its just like any other resort. Is that true?
Depends very much on where you stay, tbh.
If you book a 300 bedroom hotel, it won't be that much different from a 300 bed hotel in many other locations.
Stone town is a charming place, if that sort of vibe interests you. Some of the small hotels have beaches which are public, but because of their location are in reality private. The people are for the most part lovely.
Negatives - people don't travel after dark, even in cars. Resorts and the town itself are perfectly safe though.
If you only sit on a beach all day & sit in a pub all night, of course it seems like anywhere else!
It's what you make of it yourself really. Do your homework & you can have a truly superb holiday.
Incidentally, if you do your safari in Kenya, the agents I mentioned above can do you a couple of nights in a tree house afterwards. You can pull the bed out onto the verandah & the only sounds you'll hear are grazing animals & birds. And the occassional elephant if you're lucky! Special.