iRise reps like to say their product is designed to create "simulations" as compared to prototypes, with an emphasis on speed-of-creation and happy paths rather than high fidelity and edge cases.
At Marriott, we've used iRise effectively to demonstrate interaction flow and user experience to business sponsors. It's also been useful for conducting usability tests. Like any application, once you get a handle on the interface, you can crank out sims pretty quickly.
We used Adobe Fireworks at TheLadders to create wireframes and prototypes. By taking advantage of Fireworks' symbol functionality, we were able to develop wireframes that more closely reflected the look and feel of the site in production.
In addition to enhancing the wireframe process, Fireworks enabled rapid prototyping, which we used for usability testing and for soliciting feedback from business sponsors in support of our agile development process. Providing prototypes also minimized the amount of documentation we needed to create for our Development team.