How good is Adobe Fireworks in creating prototype mock-ups? I know of other software like Axure and Balsamiq, they come with extra cost but Adobe Web Premium includes Fireworks.
I recently left a program where one of the UX Designers used Adobe Fireworks for their mobile app mockups. He liked it a lot. It does a fine job, as long as it suits your needs and your preferences.
People use stencil sets like Keynotopia for prototyping in Keynote and/or PowerPoint as well. If a mobile platform is your destination this gives you the advantage of easily creating pseudo-working interactions with your prototype, as buttons link to different slides.
Personally, I like Omni Graffle from the Omni Group. It is similar to Visio -- which other colleagues use to great effect, but I've never gotten the hang of.
I use Fireworks mostly, but it suits more for quick sketches of couple screens or simple workflows to check if the logic is OK. The disadvantage (talking only about prototyping only) is that you still have to draw everything manually and need to update lot of screens later. Fireworks have HTML export and master pages but it definitely can not compete with software designed for prototyping. In conclusion: if you work on smaller projects with limited number of screens Fireworks fit in very well. But if you have to work on more serious project and other team members are included in this process you should consider other software.
Are you wanting to create interactive prototypes by exporting as HTML or are you just talking about wireframing in Fireworks? People often use the word mockup loosely and Balsamiq is primarily for wireframing so I wasn't sure.
I actually prefer Fireworks to Photoshop for web design so I definitely like the tool but if you're just making wireframes I'm not sure what huge advantages it would have for you.
For true interactive protoypes, I'm currently using Axure in my day job but have also used Invision to turn JPGs into prototypes with success. Invision is free for 1 project and works well with mobile too. If Axure is too steep for you check out Flairbuilder. Has a lot in common with Balsamiq and it's not perfect, but it is more focused on prototyping and interaction. If this is a task you'll be doing a lot, it may be worth a little money to purchase a tool more suited for the task at hand rather than wasting your time struggling with a tool that wasn't built for prototyping.
It all depends on your definition of 'prototype' and the needs of your UX group, your client, and your dev team and the needs of the particular project.
In otherwords, it's a really hard question to answer broadly. There are pros and cons to every type of prototype path and they vary wildly based on the particular project environment.
I recommend Flash. I find it way simpler and more intuitive - like Fireworks and Illustrator but without all the bells and whistles. Plus you get more flexibility with the multidimensional timeline (layers and frames), as well as ActionScript for your more advanced needs.
Flash for vectors and Photoshop for bitmaps.