Disclaimer: All writing is hard. All writing is easy. Um, yeah......
The hard thing about writing picture books (if you are not the illustrator) is that you don't necessarily tell all of the story. You tell most of the story, you provide the guts of the story, the flashy words and language for the story, but you must also leave a bit of mystery in the writing, so that the illustrator can do their job. The text should need the pictures as much as the pictures need the text.
Which makes getting feedback on a PB kind of hard, and the selling of a PB manuscript even more subjective than other types of writing.
First off, if you want feedback, your readers must be people who read a lot of picture books......either kids or teachers or parents or librarians or those rare souls who just really love PBs (these are some of the most wonderful folks in the world). They can tell you if you are off the mark.
Second, the subjective part on selling the idea is HUGE! What is one editor's been-there-done-that manuscript screams with possibilities to another. After all, think about it. When the editor reads a PB manuscript, it has to create a vision in her mind. It has to make her think, "Wow, if I paired this writing with so-and-so's artwork, hmm......we just might have something here."
Selling the text of a picture book is like trying to sell a dream.
Actually, writing the text is like trying to capture that dream that you had last night and can only slightly remember because your brain is still foggy from sleep but you can see it, hiding right behind your left-eye in your brain and if you could only capture it.........
......before it disappears altogether.