Know of a solid storyboarding app?

I knew that Celtx has a storyboarding app for iOS called "Celtx Shots" for free. The downside to this app is you can free draw; you can only create lines, arrows, circles, rectangles, and text. It also does include a number of preloaded pictures (i.e. people, trains, cars, lights, arrows) for the type of people that aren't so good when it comes drawing such as myself. You can always get another app that lets you draw and then load it out as a picture and import it into that app so you have them all in the same area. But if you're going to go with android tablet, there is an app called Storyboard Studio for $4.99 which has much of the same functions as Celtx Shots but allows you to free draw.

I've tried a few including:
ToonBoon Studio (Ok, but felt like it was still more for Flash type animations)
Frame Forge - Good for someone who really wants to focus on Storyboarding, but not if you're just trying to get things mocked up to show a DP.

I've been using Google Sketchup for a few years now mainly because I can download a model of pretty much anything, type of person/animal, vehicle, or building I need. There are a ton of models (almost all of IKEA's furniture is there) so it's very quick to put together a home interior and put a camera in. I export out either the stills or short videos to an NLE and cut an animatic for clients or DP's to see.

Can take a day to get your head into how to get everything positioned and move the cameras around, but once you've got it down, you can move pretty quickly and produce a lot of storyboard content. And it's free.

You can use StoryO from Jungle software. Is good.