I have the Planet on Feedly.
I find the Planet almost perfectly on-topic. Badly off-topic posts are very rare. This is very good.
There are many posts that are too technical and only people who are well-familiar with the Mozilla source code and engineering culture can find them interesting. I identify them by the title, and skip most of them, but I’m nevertheless happy that they are there because at least once a week or so there are posts of this kind which I do find interesting.
Updates from executives and big product managers (Mitchell, Asa, etc.) are usually all interesting.
Posts from extensions developers who get grumpy about major changes that require them to rewrite the extensions are great, too; they are sometimes angry, but they are passionate in a very good way.
So there. No complaints, really. If it stays as is, I’ll be quite happy.