My team and I currently use Dreamweaver, but we're rethinking our UX process now and we're exploring new tools. We decided on Balsamiq for low fidelity. What do you recommend for high fidelity tools?
There really is no universal answer to this. The fidelity needed for any particular project is going to vary from project to project.
My personal preferences is that low fidelity prototyping happen on paper (I call Balsamiq 'digital paper' and think it's a decent option). Then for high fidelity, I say get to building...get the HTML/CSS/JS going and start polishing up the interactions you need to prototype.
The reason I prefer that is that I've found mid-level fidelity prototyping tends to attract the wrong attention for both ends...clients start thinking it's the final product and start worrying about look and feel and fonts and colors. The UX team starts thinking it's the final product and doesn't take that final step of thinking through all the tiny details of every interaction that often don't make themselves apparent until you start actually building them. The design process shouldn't end until the code is in production. I find that automated prototyping tools for the 'high fidelity' stage tend to create a wall too soon in the process and the final production code and interactions suffer a bit because of that.
I use Inkscape for high fidelity mockups, from 1 to 100+ screens, especially for web, touch screen and embedded devices.
I also use Qt Designer for mocking up some desktop and embedded apps as it quickly generates me an interactive screen and I can customize the appearance using css, and as @DA01 says if you can design in a tool which gives you a leg up to actual development or prototype then all the better, and that will depend on the project and target platform.
However, you'll probably get a different answer from each person who replies! They will probably include Illustrator, CorelDraw, OmniGraffle and a variety of more targeted UI builders and IDE visual designer - depending on what each person is most comfortable with.
I think the key is that you use something where you can express your every intention and get across all the design intentions you have in mind down to every rounded corner radius, without any limitations or forced direction from the tools being used.
Your design tool should feel like an extension of your arm, letting your 'creative' flow from mind to screen. Everybody's mind - and their arm is different!
With a recent project the client did not want endless mock-ups and 'how it is going to look' proposals to sign off. Neither did they want overly detailed scoping documents that they knew were not going to be stuck to.
Already they had seen some of our work and they wanted the same functionality as an existing project, albeit improved for them with their logo, their colour scheme and their content.
Hence, for this project there were no user-experience journeys or Photoshop mockups, the existing - and functional - project provided all of the answers they needed to give us the job - 'I want one of those please'. This gave us time to spend on touches to make their version special, rather than a knock-off of what they had seen already. It also means that we are able to put in a lot more time testing, testing and more testing. During this testing considerable attention to detail can be put in.
To conclude, the best 'high-fidelity' tool for the project may not be a tool sold as such, it can be your CMS or eCommerce package.