I don't play the $30s yet but from everyone that I have spoken to about the HUSNG world. They have stated that its best to grind where you are comfortable and when your ready to move up, you will. At these stakes its more important to get your game down and your head leveled.

To respond to your question directly. I couldn't imagine the 30s being more difficult than the 20s or the 10s. I've even heard some regs say that the opponents you face dont even really improve until the 100s. Again, I havent played this high. Just passing on info from when I had these same q's.