+1 for this. I came across the same issue and opted for using php.js’s unserialize function as I didn’t want to hack the plugin. But it would be great if this could be rolled into the plugin itself so no third party JS libraries are needed, as the OP suggests.
append count=-1 at the end of your json call:
[server url]/?json=get_recent_posts&post_type=[custom type]&count=-1
