I don't know pedagogy, but I like that objects have names and properties, which is concrete and comes from the physical world (and our language). However, I find some things about the language, environment, and also tutorials rather confusing.
In the shapes tutorial, for example, we name an object that doesn't exist yet. We also name the object "cherry", which is also a word for an object in English. We write [melon color is 'yellow'] when the object named "melon" is actually red. I also wonder why there is no visual indication of which object is which (why not label the objects with their name?).
More fundamentally, in Isla each text block is a command. Why are there no actions words (at least in these initial commands)? Just like objects, names, and properties are first class syntactic citizens, so should actions. I think this would clear up some of the weirdness above.
# make circle named bob
# set bob color RED
# print bob color
... RED
# print bob
... circle
# move bob RIGHT
# make square named alice
# trash bob
# copy alice named chris
# make circle named alice
... oops, alice already exists!
# print dan
... oops, dan doesn't exist!