I actually quite like ScetchFlow, have worked with it now for about 2 months and i like that i give you a seamless transitions from click screen prototypes, to introducing behavior and states (without coding) to actual coding if that should be needed. All the while you can upload prototypes to share them online, where testers can write comments, paint on the actual screens which is syndicated back into the designer software, pretty painless. However of course there is a downside as well, you need to buy MS Expression Blend 4 to get sketch flow, which probably isn’t that cheap from an indie perspective. We are in the biz spark program, so we get free M$ stuff, which made the decision easier for us, plus we do pretty all of our dev in .net, so that was an added bonus. Haven’t had time to try our Fusion yet, anyone else got XP with that one? Hope this helped a bit 