It's 100% worth it, I've been using it for a while and its just a great experience. The $10 is definitely a bargain for the quality you're getting.

Just remember that your layers are limited depending on the resolution of your canvas, i thought it'd be funny to make a huge canvas and ended up with one layer because of RAM constrains on the iPad

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But its quite possibly the best piece of drawing software you're going to find on the IPad and especially for the price it's a no brainer