hey how come there's no adobe flash in that poll?
it's actually quite convenient prototyping websites in flash. it's universal, simple and intuitive. you can organize designs in layers and timelines, as well as a library for effective, object-oriented re-use. being vector-based, it gets real easy when you need to extend your designs on to other mediums. it's no problem achieving pixel-perfectness either, just give your design elements whole-numbered sizes and positions, and you're good to go. the actionscripting and animation features may be considered an added bonus. if i recall correctly, bbc radio just reported on how more and more people are starting to use flash for all kinds of purposes.
ofcourse, you still have to use photoshop for photographs, and illustrator for fancy artwork. but this is exactly what adobe wants -- had they bundled everything in under a single program, surely they'd lose money.