Looking for Itinerary feedback

A bit too much Bruges/Brugge in my opinion..

Personally I find Brugge too Disney-like, but two and a half days for Brugge and Gent combined isn't too much.
Enkhuizen is a beauty. Don't limit yourself to the Zuiderzeemuseum, but wander around.
The Muiderslot is for a large part a nineteenth-century reconstruction and wouldn't keep you busy the whole day. Combine it with Weesp (a 30-min direct bus connection from the Muiderslot; frequent train connections to Amsterdam), which is nicer than you would probably imagine.
It isn't clear to me how you plan your accommodation in the Netherlands, but Haarlem is only 15 mins from Amsterdam. Consider staying the first (or second) time in lively and historical Leiden. It is close to Schiphol airport (20 mins), The Hague (10 mins) and Delft (10 mins from Den Haag Centraal), and has the Keukenhof Express bus to bring you to the gardens.

Itinerary looks good to me!

Muiderslot is worth visiting (if you enjoy biking this might be a fun place to visit by bike) and if you enjoy castles and historic houses there are a number of other places to visit in and around Amsterdam. I can heartily recommend the Museum van Loon, a seventeenth-century canal house that is owned by one of the descendants of the original signatories of the charter of the VOC, the most successful European East India Company and the first MNC with shares in the world. It gives a wonderful glimpse into the life of the Dutch merchant elite and how they lived in the 18th/19th centuries. The Portuguese Synagogue and Jewish Historical Museum are also worth your time. Don't forget to visit the Rijksmuseum, Stedelijk and Van Gogh, although there are many other museums also worth visiting.

I concur that Weesp is definitely worth visiting as are Enkhuizen and Hoorn (also important VOC towns back in the day). If the weather is good you should also try to get out on a boat on the canals. Those Dam Boat Guys get good reviews although I cannot vouch for them personally.

What are you hoping to see while you are here and what are your interests?

Half a day in Den Haag could be too short it has several excellent museums but thins are a bit spread out. The Geementemuseum features the work of Piet Mondrian and is superb if you like minimalism and abstract art. I liked its colour scheme so much that I used it as the basis for my kitchen design!

As others have said getting between Haarlem and Amsterdam is very fast. We have stayed in both Amsterdam and Haarlem and much preferred Haarlem as it has canals and cobbled but not the drunk and druggie vibe of Amsterdam.