I appreciate 5.3 is not even in beta yet, but I get the impression some people are using it already, and already we are hearing "don't do this, it will break when 5.3 comes out", so I had a look at the version from the 9th, and have a few comments (in the hope someone takes notice before things are set in stone...).
Look-and-feel: I like it. In particular, the bigger text input box, and the way the right panes expand automatically to allow for any number of verbs are significant improvements.
Debugger: Very useful addition.
Fonts: Excellent, and so easy to use too.
Log: No idea how to use this.
HTML developer Tools: Looks good, no idea what it does, hope it will be documented properly when 5.3 comes out.
Replace (in code view): Great.
Clone method: Excellent addition.
Changing POV: Not played with it at all, but assuming it works, a good addition.
Difficulty rating: I would call this "cruelty", given it uses the cruelty scale. A game could be very difficult, but still be merciful.
CTRL-F4: Pressing this while playing the game only works when the focus is in the left pane, looks like a bug to me.
Lit objects: In my opinion this option should go on the Opotions tab. I originally I was going to write that it was missing because it is hidden amongst other stuff and I could not find it. On the options tab it will be clearer, and just makes sense there.
Disappointed that:
Still loses HTML comments.
Still loses inventoryverbs/displayverbs on types (frankly, this is a bug)
Still cannot edit libraries
Still no player comments
However, the big problem to me is the error response if a function is not recognised. In 5.2, we got:
Failed to load game.
The following errors occurred:
Error: Error adding script attribute 'script' to element 'testcom': Function not found: 'MoveObject2'
Tells the author what was not recognised, and where the fault was. In 5.3:
Error launching game: Object reference not set to an instance of an object.
No clue about what, no clue about where and your average user will have no idea what it means even.